ORIGINAL ARTICLE

A framework for karst ecohydrology

Ognjen Bonacci Æ Tanja Pipan Æ David C. Culver

Received: 9 June 2007 / Accepted: 6 January 2008 / Published online: 23 January 2008

� Springer-Verlag 2008

Abstract Ecohydrology can be defined as the science of

integrating hydrological and biological processes over

varied spatial and temporal scales. There exists in karst a

strong and direct interaction between the circulation and

storage of groundwater and surface water. These fluxes in

turn affect the spatial distribution of organisms in these

habitats. Because of the fact that the appearance, storage

and circulation of water in karstified areas is significantly

different from other more homogenous and isotropic ter-

rains, karst ecohydrology should develop original methods

and approaches. At the same time, traditional approaches

are also very useful. Large karst underground geomor-

phological patterns occur in many sizes and varieties,

ranging from a few meters long or deep to very large, the

deepest being deeper than 1 km and longer than hundreds

of kilometres. In this article, special attention is paid to

ecohydrological functions of karst underground features

(caves, pits, conduits, etc.), which play a crucial dual role

in (1) hydrology and hydrogeology of water circulation and

storage and (2) ecology of many rare and endangered

species. Differences in morphology, hydrology, hydroge-

ology and climate have resulted in a range of different

environments, which provide the opportunity for the

coexistence of different species. The role of the epikarst

and vadose zones, as well as caves in ecohydrological

processes, is discussed. The importance of the flood factor

in karst ecology is analysed. The aim of this article is to

move forward the discussion among different disciplines to

promote and develop a conceptual framework for karst

ecohydrology.

Keywords Karst ecohydrology � Epikarst � Cave �Subterranean habitat

Introduction

The dramatic degradation of global water resources during

the 20th and 21st century has forced environmental and

geoscientists to focus and intensify their research on inte-

gration of biological processes with hydrology. The pattern

and intensity of hydrological variability significantly

influences biotic structure and activity. On the other hand,

biotic structures may regulate abiotic ones. As a result of

these interrelationships, a new concept called ecohydrology

(Zalewski et al. 1997) has emerged. During the last two

decades, the concept of ecohydrology has appeared in

many scientific books, journals, workshops and confer-

ences dealing with hydrology, hydrogeology, water

resources management, etc. Its rapid development is a

consequence of the fact that complex scientific questions as

well as environmental problems can be effectively solved

only if several scientific disciplines (in this case at least

ecology and hydrology) are considered jointly.

For Bonell (2002), ecohydrology was the coupling of

landscape processes with hydrobiology. Because of the

particularities of water circulation in karst areas, the

O. Bonacci (&)

Faculty of Civil Engineering and Architecture,

University of Split, Matice hrvatske 15, 21000 Split, Croatia

e-mail: obonacci@gradst.hr

T. Pipan

Karst Research Institute, ZRC-SAZU,

Postojna SI-6230 Postojna, Slovenia

e-mail: pipan@zrc-sazu.si

D. C. Culver

Department of Biology, American University,

4400 Massachusetts Ave. NW, Washington DC 20016, USA

e-mail: dculver@american.edu

123

Environ Geol (2009) 56:891–900

DOI 10.1007/s00254-008-1189-0

coupling of surface water–groundwater processes is the

most important prerequisite for understanding constraints

on sustainable development. Karst ecohydrology intends to

integrate not only landscape with groundwater hydrology

but also with freshwater biology.

The karst environment has very different characteristics

than all other environments have. Water circulation in karst

areas is different from that in non-karst areas, which is the

main reason for the strongly different characteristics of

karst and non-karst hydrology as well as karst ecohydrol-

ogy. Because the appearance, storage and circulation of

water in karst is significantly different from that in other

more homogenous and isotropic terrains, karst ecohydrol-

ogy should develop original methods and approaches. With

the exception of a very few caves (Sarbu et al. 1996) and

deep subsurface habitats (Culver and Pipan 2007), there is

no primary production in subsurface environments, and

subterranean aquatic communities are based on allochton-

ous sources of carbon. Many deep subterranean aquatic

habitats are energy-poor, but many superficial subterranean

habitats have significant amounts of carbon (Simon et al.

2007). Knowledge of basic concepts about surface and

underground karst landforms and ecology in karst terrains

is fundamental to an integrated sustainable management of

very valuable and vulnerable karst biological and water

resources.

The article describes the basic ecological and hydro-

logical concepts of karst terrains to enable easy

understanding of the processes that determine the behav-

iour of water circulation in karst and its influence on the

associated ecosystems. The aim is to shed more light on the

integral analysis of hydrologic and ecologic aspects in karst

terrains. Perhaps, this article will encourage public scien-

tific and professional discussions that should lead to a more

complete explanation and development of the concept

framework of karst ecohydrology.

Definition of ecohydrology

Scientists do not agree on the details of the definition,

importance, future development and role of ecohydrology,

but they agree that cooperation between hydrology and

ecology could help in solving many critical problems

dealing with sustainable development and ecosystem

management. Ecohydrology tries to understand, explain

and use links between ecology and hydrology. It integrates

landscape hydrology with freshwater biology.

Developing the research interface between hydrology

and ecology has been recognised as a research frontier in

geosciences (Bond 2003). Despite a history of research that

integrates insight from the two scientific disciplines, they

still operate somewhat independently with different

philosophies, conceptual frameworks, terminology and

experimental approaches (Hannah et al. 2004).

Harte (2002) seeks a synthesis of what he calls the

Newtonian and Darwinian approaches to science. He

believes that such a synthesis offers opportunities for

progress at the intersection of physics and ecology where

many critical issues in earth system science reside. Harte

(2002) explains it this way: ‘‘Physicists seek simplicity in

universal laws. Ecologists revel in complex interdepen-

dencies. A sustainable future for our planet will probably

require a look at life from both sides. Physicists and

ecologists approach their crafts from different intellectual

traditions, as exemplified by the differing values they

attach to the search for simplification and universality. As a

particle theorist by training, currently engaged in the study

of ecology and global change, I have witnessed dysfunc-

tional consequences of this bimodal legacy.’’

Hydrological processes involve flows of matter and

energy (water, nutrients, sediments, species, seeds, heat,

etc.) between different landscape components. The spatial

structure and temporal dynamics of pathways of connec-

tivity are usually driven by climatic factors and are

mediated by catchment characteristics (Soulsby et al.

2006). This connectivity exists at different spatial and

temporal scales. It is extremely variable, and until now its

role in ecosystem function is not well understood. This

connectivity is especially important in karst areas, because

of their extreme surface and underground morphological

complexity and connectivity.

Zalewski (2002) holds that ecohydrology uses hydro-

logical and ecological processes for sustainable manage-

ment of water resources. For Nuttle (2002), ecohydrology

is the subdiscipline shared by the ecological and hydro-

logical sciences that is concerned with the effects of

hydrological processes on the distribution, structure and

function of ecosystems, and on the effects of biotic pro-

cesses on elements on the water cycle.

Ecohydrology can be understood as one branch of ‘‘non-

engineering’’ hydrology, which is developed from forest

hydrology, wetland hydrology, landscape hydrology, lake

hydrology, etc. It seems that an acceptable definition of

ecohydrology would be as follows: ‘‘Ecohydrology is the

science of integrating hydrological processes with biota

dynamics over varied spatial and temporal scales.’’

Ecohydrology is in a very early phase of formation.

Because of this, it offers many scientific challenges and

possibilities for exciting, hardly foreseen and dynamic

development. Ecohydrology has potential to provide sci-

entists with environmental-friendly and sustainable

solutions to several problems related to water quantity,

flooding and pollution. Karst as a specific landscape and

environment for its sustainable development and protection

definitely needs new achievements in ecohydrology. It

892 Environ Geol (2009) 56:891–900

123

needs specific approaches to ecohydrology, i.e., it needs

karst ecohydrology.

Karst, karst hydrology and/or karst hydrogeology

Karst is the type of landscape found on carbonate rocks or

evaporates. The carbonate rocks, limestone and dolomite

are the principal sites of dissolutional caves and karst

landforms (Ford 2004). The highly varied interactions

among chemical, physical and biological processes have a

broad range of geological effects including dissolution,

precipitation, sedimentation and ground subsidence. Karst

is defined as a terrain, generally underlain by limestone or

dolomite, in which the topography is chiefly formed by the

dissolving of rock, and which is characterised by sinkholes,

sinking streams, closed depressions, subterranean drainage

and caves (Field 2002). A wide range of closed surface

depressions, a well-developed underground drainage sys-

tem, and a strong interaction between circulation of surface

water and groundwater typify karst.

Carbonate rocks are more soluble than many other

rocks. They are subject to a number of geomorphological

processes. The processes involved in the weathering and

erosion of carbonate rocks are many and diverse. The

varied and often spectacular surface landforms are merely a

guide to the presence of unpredictable conduits, fissures

and cavities beneath the ground. These subsurface features

can occur even where surface karstic landforms are com-

pletely absent. In soluble rock terrains, more so than in

most other terrains, the unexpected should always be

expected (Atkinson 1986).

Karstification is a geological characteristic important for

water circulation and storage. It can be delineated through

the density, frequency and number of all types of karst

voids (intergranular voids, pores, joints, cracks, fractures,

fissures, conduits and caves). Generally, it is greatest near

the surface and decreases with the depth of a karst massif.

Karstification is a continuous process governed by natural

and man-made interventions.

In rock types favoring dissolution by groundwater, the

most active flow routes become enlarged over time,

resulting in a highly heterogeneous and anisotropic karst

aquifer (Smart and Worthington 2004a).

Karst aquifers are some of the most complex and diffi-

cult systems to decipher. The highly heterogeneous nature

of karst aquifers leads to the inability to predict ground-

water flow and contaminant transport direction and travel

times. For different scientists (hydrologists, hydrogeolo-

gists, geochemists, geomorphologists, hydraulic engineers,

geographers, geophysicists, speleologists, biologists, ecol-

ogists, etc.), this represents a challenging interplay of water

flow and storage in large caves and conduits and very small

fractures and pores. Circulation of groundwater in karst

aquifers is quite different from water circulation in other

non-karstic type aquifers. In karst aquifers, water is col-

lected in networks of interconnected poorly integrated

solution pockets at the top of karst (epikarst), cracks and

fissures, and channels with streams. Hydraulic permeability

of karst aquifers is essentially created by flowing water and

has anisotropic character. Karst aquifers, because of their

unique hydrologic and hydrogeologic characteristics, are

extremely susceptible to contamination.

Interactions between surface and subsurface in karst are

very strong (Bonacci 1987). In karst ecohydrological

investigations, the basic problem is that subsurface water is

highly heterogeneous in terms of location of conduits,

location of vertically moving water and flow velocities.

The surface and especially subterranean environment in

karst provide a range of habitats with different chemical

and biological processes. To biologists and ecologists, they

are fragile ecosystems, hosting rare and endangered spe-

cies. For geochemists, they are the routes of rapid transport

of contaminants.

Karst aquifers are a triple porosity system consisting of

the following: (1) matrix permeability; (2) fracture per-

meability; (3) conduit permeability. Matrix permeability is

a complex of voids in a small rock fragment. The matrix

consists not only of intergranular pores but also of micro-

fissures and small karst voids. Fracture permeability is

formed from mechanical joints, joint swarms and bedding

plane partings, enlarged by solution. Conduit permeability

is represented by pipe-like openings with apertures ranging

from 1 cm to a few tens of metres (White 2002). In this

complex system of voids, there are a variety of different

microhabitats, for subterranean species, both aquatic and

terrestrial.

The relationship between joint frequency and porosity is

a crucial one. High porosity and permeability lead to a

more uniform flow of water through karstified rock, mak-

ing the presence of joints less important as flow routes. The

characteristic features of karst aquifers are the conduits,

which provide low resistance pathways for groundwater

flow. Conduit flow often has more in common with surface

water than with groundwater flow. Worthington (1999)

mentions that it has often been considered that there is a

range in carbonate aquifers between ‘‘karstic’’ and ‘‘non-

karstic’’ end members. This fact can have strong influence

on karst biota development. Because of these reasons, karst

hydrology requires an integration of surface water and

groundwater concepts.

There are three zones of water circulation in karst (Ford

and Williams 2007): (1) the unsaturated, or vadose zone,

the zone of vertical circulation; (2) intermittently saturated

or epiphreatic zone; (3) phreatic zone. From the ecological

point of view, the role of vadose zone, including epikarst,

Environ Geol (2009) 56:891–900 893

123

is extremely important. The vadose zone with a karst

aquifer forms a two-component system in which the major

part of storage is in the form of true groundwater in narrow

fissures, where diffuse and laminar flow prevails. On the

other hand, the majority of water is transmitted through the

karst underground by turbulent flows in solutionally

enlarged conduits in the epiphreatic zone.

The chemical composition of water in karst plays a

crucial role not only in dissolution and deposition but also

in ecological processes. A chemograph plots the changes

in chemical parameters as a function of time and can be

compared with the hydrograph. Their response times are

different, i.e., the chemograph and the hydrograph are not

in phase. Water discharging from diffuse flow springs

tends to have relatively little variation in water chemistry

with discharge or season. In contrast, water moving

through carbonate rock, conduit flow aquifer system can

have a residence time as short as hours or days, which is

generally insufficient for chemical equilibrium (Langmuir

1971). As a result, waters emerging from conduit system

springs can have highly variable chemistry (Raeisi et al.

2007).

Figure 1 shows three different types of karst fissure

system development: (1) existence of highly developed and

interconnected large karst conduits and narrow karst fis-

sures (combined system); (2) existence of only narrow

karst fissures with slow laminar flow (diffuse system); (3)

existence of only large karst conduits with fast turbulent

flow (conduit system). Figure 2 presents the outflow dis-

charge hydrographs and chemographs of karst springs

discharging from three different karst fissure systems

shown in Fig. 2 as a reaction to the same rainfall (Bonacci

1993).

Biological importance and specificities of karst

Most karst landforms are actually products of both biotic

and abiotic processes operating concurrently in intricate

interrelationships (Tabarosi 2002). Karst features that are

thought to be directly related to organic processes have

been termed phytokarst or biokarst. It refers to extremely

jaggedly dissected limestone pinnacles in the Cayman

Island (Folk et al. 1973). This term was later applied to a

variety of dissimilar features (i.e., stromatolites). The term

biokarst refers to erosional and depositional karst features

produced by direct biological action (Viles 1984). The

effects of living organisms on karst geomorphology are

profound at an ecosystem scale, and they are widespread,

intense, diverse and of fundamental importance (Tabarosi

2002). The evolution of entire karst landscapes is thought

to be biologically controlled through the interrelationships

of vegetative cover, erosion and dissolution rates (Hupp

et al. 1995). Barrany-Kevei (1992) has suggested that the

process of karstification is essentially of biogenic character.

Rouch (1977) first stated that a karst basin is a clearly

definable ecosystem with measurable surface inputs from

sinking streams and rainfall infiltration, and measurable

outputs at the resurgence including biological parameters.

Typically, subterranean food webs are truncated at both

ends (Gibert and Deharveng 2002) because of the absence

of photosynthesis and secondary predators. Of course, in

chemoautotropohic systems, only the predator end is

truncated. Healthy and diverse karst ecosystems provide

important goods and services as important foundations for

all aspects of sustainable development. The ecosystem

services are the benefits that people obtain from ecosys-

tems. These include provisioning, regulating, and cultural

services that directly affect people, and the supporting

services needed to maintain other services (WMO 2006).

Fig. 1 Three different types of karst fissure system development: acombined; b diffuse; c conduit

894 Environ Geol (2009) 56:891–900

123

Many of these services are closely interlinked. Many of the

services provided by karst ecosystems result from the

biological activity of the diverse assemblages of organisms

found within those systems, especially microorganisms

(Herman et al. 2001).

Smart and Worthington (2004b) stress that in karst

environments, water tracing finds particular value in

defining the path followed by inaccessible underground

streams, which could be the dispersal paths of organisms as

well. For development of karst ecohydrology, experience

obtained with the long history of use of subterranean fauna

as groundwater tracers could be very useful (Kranjc 1997;

Kass 1998; Pipan and Culver 2007).

Karst ecosystems are sensitive to environmental chan-

ges. The importance of maintaining biological diversity

goes far beyond mere protection of endangered species and

beautiful landscape. In the Yucatan karst in Mexico, Bed-

dows (2004) states that groundwater resources and the

anchialine cave habitat (known to host at least 37 stygo-

biotic species) may be degraded by disposal wells that

pump sewage effluent into the saline zone, while cess pits

and garbage dumps leach into the freshwater lens from

above. It is necessary to obtain a thorough understanding of

how aquatic and terrestrial ecosystems function and inter-

act in very complex, vulnerable and in time and space

extremely dynamic karst systems. Figure 3 (WMO 2006)

shows various components essential in deterring biological

diversity.

Karst ecosystem analysis should be focused on the flow

of energy and the cycling of nutrients through biotic and

abiotic components of the system. There are widespread

hydrological, chemical and biological differences in the

vadose plus epikarst, epiphreatic, and phreatic components

as well as within each component. Gibert et al. (1994)

mention that every karst ecosystem model differs (among

karst models) in fundamental ways including major dif-

ferences in its fauna. It should be stressed that the fauna

does not cause the differences. One of the basic reasons for

this is that water in karst underground is highly heteroge-

neous in terms of location of large underground spaces

(caves and conduits), location of vertically moving sub-

surface water in vadose zone and flow velocities as well as

in its chemical composition.

Cave ecosystems generally depend on organic carbon

entering from outside. In caves, there are two sources of

organic matter—vertically percolating water from the

epikarst and from sinking streams. In both cases, it is

dissolved organic carbon (DOC), an important energy

source, but in many caves coarse particulate organic mat-

ter, including leaves, twigs are also important (Simon and

Benfield 2001). However, even with extensive coarse

organic matter inputs, DOC is the most important in

forming the base of subterranean food webs (Simon et al.

2007). In some situations there are other inputs. In some

caves bat guano is important (Graening and Brown 2003).

However, the most interesting energy source found in only

a few caves is chemoautotrophy. In Movile Cave

(Romania), bacteria derive energy from sulphur and iron

minerals (Sarbu et al. 1996). The essential aspect of

Fig. 2 Various forms of discharge hydrograph (Q) and water

hardness (WH) as a reaction on the same rainfall (P) from the three

different karst fissure systems shown in Fig. 1

BIOLOGICAL DIVERSITY

Adequate water quality

Appropriate amount andvariability of water

Habitiat diversity

Spatial heterogeneity

Sediment regime

Temporal variability

Flow regime

Lateral, vertical and longitudinal connectivity

Fig. 3 Components essential for formulation of biological diversity

(WMO 2006)

Environ Geol (2009) 56:891–900 895

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chemoautotrophy is that the energy of chemical bonds is

converted to a biologically useful form, particularly aden-

osine triphosphate (ATP). The best-documented example

of chemoautotrophy from a subterranean environment

involves the following reaction:

H2Sþ 2O2 ! SO2�4 þ 2Hþ

where hydrogen sulfide is oxidised to form sulfuric acid. In

Movile Cave, the reaction is mediated by the bacterium

Thiobacillus thioparus (Vlasceanu et al. 1997). The reac-

tion is energy producing, with a Gibbs free energy (DG) of

-798.2 kJ/mole.

Based on an educated guess and ‘‘back to the envelope

calculations,’’ Culver and Holsinger (1992) estimate that

between 20,000 and 100,000 species of animals worldwide

live exclusively in caves, about one-third of which are

aquatic. Of course the number of described species is much

less, but nonetheless impressive. For example, Derharveng

et al. (2008) report 930 stygobiotic species from six

European countries (Belgium, France, Italy, Portugal,

Slovenia and Spain). On a smaller geographic scale, Pipan

and Culver (2007) report 37 epikarstic copepods and esti-

mate that another eight remains to be discovered. Hotspots

of terrestrial cave biodiversity lie along a mid-temperate

ridge of maximum primary productivity, e.g., along the

Pyrenees and the French–Spanish border (Culver et al.

2006). The western Balkans (also on Culver et al.’s ridge)

are biodiversity for both aquatic and terrestrial species

(Sket et al. 2004).

Many of those species are limited to a single cave or to a

handful of caves in one highly circumscribed area. Fig-

ures 4, 5, and 6 show examples of aquatic and terrestrial

obligate subterranean dwellers.

In sediments, which are transported by water through the

karst underground, there are many nutrients essential for

species living in these spaces. Because of large conduits

and fast flow velocities, karst aquifers carry more sediment

than other media aquifers carry. Sediment concentrations

increased with storm-induced discharges, and most parti-

cles, nutrients as well as microbes, different kind of

pollutants and bacteria attached to particles are transported.

Sediment transport has the potential to mobilise metals and

toxic organics in karst aquifers by sorbing them on surfaces

that are mobile instead of immobile. Particles not only have

potential to co-transport contaminants, but in the case of

microbes, they may be contaminants.

Habitats in karst

Subterranean aquatic ecosystems include a wide variety of

aphotic habitats such as cave streams, epikarst, phreatic

water, springs and interstitial habitats. In the vadose zone,

there is epikarst, percolating water and drip pools. In epi-

phreatic zone, it is cave streams (riffles and pools). In

phreatic water it is primarily lakes.Fig. 4 Proteus anguinus, an obligate aquatic subterranean salaman-

der species from Dinaric karst (Photo: J. Hajna)

Fig. 5 Leptodirus hochenwartii reticulates is an obligate terrestrial

subterranean beetle species from south-west Dinaric karst (Photo: S.

Polak)

Fig. 6 Precopulatory mating individuals of Bryocamptus zschokkeicopepods found in dripping water (Photo: T. Pipan)

896 Environ Geol (2009) 56:891–900

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Howarth (1983) states that cave habitats are strongly

zonal. He recognised five terrestrial zones: (1) entrance; (2)

twilight; (3) transition; (4) deep; (5) stagnant air. This

classification emphasises the transition between surface

and subsurface. The surface and underground environ-

ments meet in the entrance zone. The twilight zone extends

from the boundary of plant life to the limit of light. The

transition zone is in total darkness but is subjected to

nocturnal desiccating winds caused by cold air sinking into

the cave. The deep zone, which Culver (2001) called the

dark zone, is characterised by total darkness and long-term

presence of moisture and saturated atmosphere. The stag-

nant air zone lies beyond the deep zone and only slowly

exchanges air with surface (Howarth 2004).

It should be stressed that there are more or less many

different karst subterranean habitats. For example, Jones

et al. (2003) include voids in the soil, dry spaces under

talus slopes, the underflow zone of stream channels and

interstitial openings in the primary rock matrix. Maybe,

development of karst ecohydrology concept will help in

formation of one consistent karst hypogean habitats clas-

sification. We focus on what are perhaps the three most

ubiquitous and important aquatic habitats in subterranean

karst: (1) epikarstic zone; (2) caves; (3) drip pools con-

nected with water trickles.

The epikarst or subcutaneous zone (Williams 1983)

represents boundary zone between soil and rock in karst

terrains, and has been called the skin of karst (Bakalowicz

2004). It is analogous to the regolith in non-karst areas, but

with considerable solutional modification. It is aerated and

non-saturated habitat with a considerable storage capacity

where the water generally flows vertically to the epiphre-

atic. After heavy rainfall, water flow within this zone very

often displays a significant lateral component. Epikarst

performs hydrological functions, acting as a sponge,

soaking up water during wet periods and releasing it during

dry periods. This zone represents a large reservoir where

the water can be stored for a certain period of time, which

may be very important for surviving of many species living

in it. Zambo (2004) states that the main site of the karst-

ecological subsystems is the epikarst.

Rainfall falling on the surface of the catchment area, soil

moisture, vegetation and air temperature on the catchment

control recharge of water through trickles. Trickles do not

respond to all types of precipitation. After long-lasting dry

periods, depending on air temperature and vegetation, the

water will manage to sink from the surface to the cave only

if the rainfall is of the order of 50 mm or more. In the wet

period, even the water resulting from rainfall of less than

10 mm manages to penetrate (Kogovsek and Habic 1980;

Kogovsek 1990; Baker and Brundson 2003; McDonald and

Drysdale 2007). This demonstrates the significant storage

capacity primarily of epikarst zone (Williams 1983).

The epikarst exists practically everywhere, both in bare

and covered karst regions. Ford and Williams (2007)

indicate that the epikarst is 3–10 m deep and can reach up

to 30 m. The karst rock features (fissures, conduits, cracks,

caves, etc.) are best developed in this narrow area. All or

many of them are filled with non-consolidated soil, very

often with terra rossa. The temperature of the epikarst is

usually lower than that of the atmosphere (Zambo 2004).

The concentration of the water moving in the epikarst large

conduits shows frequent changes. The water arriving from

the narrow fissures has a lower discharge and more uniform

carbonate concentration (Zambo 2004).

Pipan (2005) and Pipan and Culver (2007) show that

there is exceptionally rich aquatic fauna in the epikarst.

The epikarst is of interest to biologists due to its species

diversities and richness. At the same time, it is a source of

organic input as well as the location of the exchange of

surface and subsurface fauna.

For Jones et al. (2003), caves are one part of an inter-

connected complex of subsurface voids and fractures of

varying sizes that make up the hypogean or subsurface

environment. The combination of micro- and macro-sized

openings provides habitats for generally unique organisms

and serves as pathways for movement of water and

nutrients.

Cave ecosystems (aquatic and terrestrial) are open sys-

tems that rely on transport of organic matter from the

surface as an energy base of the system. This view

emphasises the intimate association between surface and

underground environments in karst areas. It also indicates

the potential of negative anthropogenic changes on the

surface to impact the subsurface karst environment. Many

of cave dwelling species are very sensitive to environ-

mental changes. Communities can be described by their

relationship to environmental variables. In this way, they

may be barometers of environmental degradation in the

whole karst basin.

In general, individual caves are not especially diverse.

Culver and Sket (2000) report only 20 caves with more

than 20 cave-limited aquatic and terrestrial species, and

only six that possess more than twenty cave-limited ter-

restrial species—troglobionts. All six are distinguished

either by their depth and complexity (Mammoth Cave in

USA, Postojna–Planina cave system in Slovenia, Vjetre-

nica Cave in Bosnia and Herzegovina) or by their abundant

food sources (Movile Cave in Romania, Bayliss Cave in

Australia, Gua Kalling–Towakkalak cave system in Indo-

nesia). It seems that more habitats and the greater food

supply give more opportunities for niche separation and

coexistence between species.

Drip pools are small water bodies, which exist in the

fossil part of the caves. Drip pools within caves are highly

heterogeneous in species composition. They are filled up

Environ Geol (2009) 56:891–900 897

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by water, which seeped down the walls or dripped directly

from the trickles situated on the cave or conduit ceiling

(Pipan 2005). There are permanent and temporary trickles,

bringing water only during the rainfall and some time after

its cessation.

Pools can be separated or connected, which depends on

hydrological conditions and their changes during the time.

Quality and quantity of recharged water strongly influence

the underground fauna composition, its diversity and

abundance. Pipan (2005) distinguishes four categories of

pools: (1) pools formed on the top of the stalagmites filled

up by direct water trickles from the ceiling; (2) pools

formed in the permanent small depressions on the bottom

of the stalagmites; (3) pools formed in the depressions on

clay; (4) pools formed in the depressions on calcite. It is

still an open question whether or not any pool populations

are source populations (population that survive in the

absence of immigration) or whether in the absence of a

continuing rain of animals from epikarst all populations

would go to extinct.

Role of floods in karst ecosystems

Floods are one of the most dramatic interactions between

human beings and the environment. Throughout history,

floods have been a part of human and nature destiny (Smith

and Ward 1998). People look at floods as a catastrophe, but

in reality floods are integral part of nature, playing a critical

role in ecosystem function. At the same time, flooding

brings many benefits particularly for ecological variability

and soil fertility. Floods as natural disturbance are widely

accepted as one of the primary driving forces behind eco-

system function. Flooding promotes exchange of materials

and organisms between habitats and plays a key role in

determining the level of biological productivity and

diversity. Those processes are especially important for

karst environment.

Hawes (1939) stresses that cave is usually supposed to

be the least changeable of all animal habitats because of its

consistently monotonous factors, such as a low and almost

constant temperature, an atmosphere continuously satu-

rated with water vapour, and permanent darkness. But as he

points out this is not correct. Flooding of karst underground

and caves appear regularly (every year) or irregularly and

more or less everywhere, affecting species living in these

areas. It means that a lot of underground karst species as

well as their habitats are regularly (minimum one time per

year) or irregularly exposed to environmental stress. The

cave and karst underground environment is not constant.

Hawes (1939) stresses the importance of floods for karst

underground environment. Floods operate as agents of

distribution, and help in maintaining a regular food supply.

As mechanical agents, they introduce species from surface

and so initiate colonisation of the karst underground. Flood

as violent periodic disturbance must have important eco-

logical effects (Hawes 1939). The recession of the waters

during dry period of year may create special food problems

by isolating animals in small pools. By carrying animals

from one to another cave, flooding accounts for certain

facts of local distribution (Hawes 1939).

Hawes (1939) gives an example of possible underground

colonisation of the karst underground in the Popovo Polje

(Trebisnjica River) in Bosnia and Herzegovina. Generally,

the cyprinid fish (Phoxinellus ghetaldii) spends most of

their time underground. Floods wash them out in great

quantities and regularly every year at the beginning of the

wet and cold period (mostly during October or November).

Breeding occurs at this time, and the young fish are left to

spend a year in the open, though their parents are carried

back into the karst underground. After the next flood, the

young fish in turn are swept into the underground. The eyes

of Phoxinellus ghetaldii are normal, but the fish exhibits a

tendency to reduce scales, which is remarkably common

among cave fishes. Hawes (1939) concludes that, maybe in

this case we are witnesses of the early stages of colonisa-

tion of caves by an epigean fish. Very probably, floods are

responsible for this process. Construction of many hydro-

technical structures within the Trebisnjica catchment

during 1970s caused huge changes in the hydrological and

hydrogeological regime, which had a negative influence on

existing ecohydrological system.

Conclusions

Karst terrains are becoming increasingly populated. Their

surface water as well as the water in their aquifers is

threatened. Along with water, the karst ecosystem is

threatened. Generally, karst is still poorly explored, and

hence the development of karst ecohydrology should be

supported. The karst system shows extreme heterogeneity

and variability of geologic, morphologic, hydrogeologic,

hydrologic, hydraulic, ecological and other parameters in

time and space. Such a complex system needs interdisci-

plinary approach. It is highly important to understand the

interaction of groundwater and surface water in karst and

their influence on surface and underground biological

processes.

Problems with water quality in karst areas are rapidly

increasing due to both point and non-point source pollu-

tion. The basic factors influencing negatively subterranean

ecosystems are as follows: (1) uncontrolled human influ-

ence on the water regime; (2) water pollution; (3)

unsustainable agriculture and forestry; (4) mass tourism in

some sites; (5) deficiency of legal framework; (6) lack of

898 Environ Geol (2009) 56:891–900

123

data on distribution of fauna and habitats; (7) lack of

protection of biological diversity. Achievements in karst

ecohydrology would help in solving some of the above-

mentioned problems. Karst ecohydrology should con-

centrate their scientific investigations efforts in critical

areas, such as the epikarst zone, caves, underground

streams and karst springs.

The survival of a karst ecosystem depends especially on

the proper protection and management of the caves and the

surrounding terrains. Development of a new conceptual

framework called karst ecohydrology should play an active

and important role in sustainable development of karst ter-

rains. Karst ecohydrology should help in understanding and

explaining of the sensitivity of different sites and their eco-

logical communities to low flow as well as flood stresses.

For understanding changes of cave faunas, simultaneous

monitoring of at least the following ecological factors is

needed: temperature, pH, dissolved oxygen, nutrient inputs,

quality and quantity of water recharge and flow, etc.

Organic carbon is probably the most interesting parameter

of all but is difficult to measure. Cave faunas change

seasonally and response to climate. The critical threats

to caves and their ecosystems come from land develop-

ment, water pollution and chemicals. Protection of the

subterranean aquatic fauna requires protection of surface

waters. In general, conservation and protection of subter-

ranean aquatic sites requires greater public awareness and

appreciation.

Karst ecohydrology should be able to answer many

important questions dealing with interactions between karst

hydrology and karst ecology. The synthesis of ecological

and hydrological approaches could expedite progress in

understanding karst environment and in this way contribute

to the development of the karst ecohydrology concept.

Karst ecohydrology can be understood as a scientific

subdiscipline concerned with the ecological and hydro-

logical processes in karst areas. Karst ecohydrologists

should study the effects of hydrological processes on the

distribution, structure and function of specific and vulner-

able karst ecosystems, and the effects of biotic processes on

elements of water cycle (hydrology). A karst ecohydro-

logical approach means integrating karst studies into a

more general ecological, biological, hydrological, hydro-

geological, geomorphological and geochemical context.

Works on karst ecohydrology brings the diverse perspec-

tive of ecologists and karst hydrologist and hydrogeologists

together.

References

Atkinson TC (1986) Soluble rock terrains. In: Fookes P, Vaughan PR

(eds) Handbook of engineering geomorphology. Chapman and

Hall, New York, pp 241–257

Bakalowicz M (2004) The epikarst, the skin of karst. In: Jones WK,

Culver DC, Herman JS (eds) Proceedings of the interdisciplinary

workshop on epikarst, Shepherdstown, West Virginia, USA, 1–4

October 2003. Karst Waters Institute, Charles Town, pp 16–22

Baker A, Brundson C (2003) Non-linearities in drip water hydrology:

an example from Stump Cross Cavern, Yorkshire. J Hydrol

277:151–163

Barrany-Kevei I (1992) Les facteurs ecologiques dans la formation du

karst. In: Salomon JN, Maire R (eds) Presses Universitaires de

Bordeaux, Bordeaux, France, pp 51–59

Beddows PA (2004) Yucatan phreas, Mexico. In: Gunn J (ed)

Encyclopedia of cave and karst science. Fitzroy Dearborn, New

York, pp 786–788

Bonacci O (1987) Karst hydrology with special reference to Dinaric

karst. Springer, Berlin, 184 pp

Bonacci O (1993) Karst springs hydrographs as indicators of karst

aquifers. Hydrol Sci J 38(1):51–62

Bonell M (2002) Ecohydrology—a completely new idea? Hydrol Sci

J 47(5):809–810

Bond B (2003) Hydrology and ecology meet—and the meeting is

good. Hydrol Process 17:2087–2089

Culver DC (2001) The dark zone. In: The sciences, vol. 41, no. 2.

New York Academy of Sciences, New York, Spring 2001, pp

30–35

Culver DC, Holsinger JR (1992) How many species of troglobites are

there? Bull Nat Speleol Soc 54:79–80

Culver DC, Deharveng L, Bedos A, Lewis JJ, Madden M, Reddell JR,

Sket B, Trontelj P, White D (2006) The mid-latitude biodiversity

ridge in terrestrial cave fauna. Ecography 29:120–128

Culver DC, Pipan T (2007) Subterranean ecosystems. In: Levin SA

(ed) Encyclopedia of biodiversity, 2nd edn. Elsevier, Amster-

dam, 19 pp doi: 10.1016 BO-12-226865-2/00262-5

Culver DC, Sket B (2000) Hotspots of subterranean biodiversity in

caves and wells. J Cave Karst Stud 62(1):11–17

Deharveng L, Stoch F, Gibert J, Bedos A, Galassi D, Zagmajster M,

Brancelj A, et al (2008) Groundwater biodiversity in Europe. In:

Gibert J, Culver DC (eds) Assessing and conserving groundwater

biodiversity. Freshwater Biology (special issue) (in press)

Field MS (2002) A lexicon of cave and karst terminology with special

reference to environmental karst hydrology. USEPA, Washing-

ton DC, 194 pp

Folk RL, Roberts HH, Moore CH (1973) Black phytokarst from Hell,

Cayman Island, British West Indies. Geol Soc Am Bull 84:2351–

2360

Ford D (2004) Carbonate karst. In: Gunn J (ed) Encyclopedia of cave

and karst science. Fitzroy Dearborn, New York, pp 184–186

Ford D, Williams P (2007) Karst hydrogeology and geomorphology.

Wiley, Chichester, 562 pp

Gibert J, Deharveng L (2002) Subterranean ecosystems: a truncated

functional biodiversity. BioScience 52:473–481

Gibert J, Stanford JA, Dole-Olivier MJ, Ward JV (1994) Basic

attributes of groundwater ecosystems and prospects for research.

In: Gibert J, Danielopol D, Stanford JA (eds) Groundwater

ecology. Academic Press, San Diego, pp 8–42

Graening GO, Brown AV (2003) Ecosystem dynamics and pollution

effects in an Ozark cave stream. J Am Water Res Assoc

39:1497–1505

Hannah DM, Wood PJ, Sadler JP (2004) Ecohydrology and hydroe-

cology: a new paradigm? Hydrol Process 18:3429–3445

Harte J (2002) Toward a synthesis of the Newtonian and Darwinian

worldviews. Phys Today 55(10):29–37

Hawes RS (1939) The flood factor in the ecology of caves. J Anim

Ecol 8(1):1–5

Herman JW, Culver DC, Salzman J (2001) Groundwater ecosystems

and the service of water purification. Stanford Environ Law J

20:479–495

Environ Geol (2009) 56:891–900 899

123

Howarth FG (1983) Ecology of cave arthropods. Ann Rev Entomol

28:365–389

Howarth FG (2004) Hawaiian islands, biospeleology. In: Gunn J (ed)

Encyclopedia of cave and karst science. Fitzroy Dearborn, New

York, pp 417–419

Hupp CR, Osterkamp WR, Howard AD (1995) Biogeomorphology,

terrestrial and freshwater systems. Geomorphology 13(1–4):1–

34

Jones WK, Hobbs III HH, Wicks CM, Currle RR, Hose LD, Kerbo

RC, Goodbar JR, Trout J (2003) Recommendations and guide-

lines for managing caves on protected lands (Karst Waters

Institute special publication 8). Karst Waters Institute, Charles

Town, 95 pp

Kass W (1998) Tracing technique in geohydrology. A.A. Balkema,

Rotterdam, 581 pp

Kogovsek J (1990) Characteristic of the precipitation infiltration

through the roof of Taborska jama. Acta Carsol 25:157–165

Kogovsek J, Habic P (1980) The study of vertical percolation of water

in the case of Postojnska jama and Planinska jama. Acta Carsol

9:129–148

Kranjc A (ed) (1997) Tracer hydrology 97. A.A. Balkema, Rotterdam,

450 pp

Langmuir D (1971) The geochemistry of some carbonate groundwa-

ters in Pennsylvania. Geochim Cosmochim Acta 35:1023–1045

McDonald J, Drysdale R (2007) Hydrology of cave drip waters at

varying bedrock depths from a karst system in southeastern

Australia. Hydrol Proc 21(13):1737–1748

Nuttle WK (2002) Is ecohydrology one idea or many? Hydrol Sci J

47(5):805–807

Pipan T (2005) Epikarst—a promising habitat. Copepod fauna, its

diversity and ecology: a case study from Slovenia (Europe).

Zalozba ZRC; Institut za Raziskovanje Krasa ZRC SAZU,

Postojna, 101 pp

Pipan T, Culver DC (2007) Epikarst communities: biodiversity

hotspots and potential water tracers. Environ Geol 53:265–269

Raeisi E, Groves C, Meiman J (2007) Effects of partial and full pipe

flow on hydrochemographs of Logsdon river, Mammoth Cave

Kentucky USA. J Hydrol 337:1–10

Rouch R (1977) Considerations sur l’ecosysteme karstique. C R Acad

Sci Paris Ser D 284:1101–1103

Sarbu SM, Kane TC, Kinkle B (1996) A chemoautotrophically based

cave ecosystem. Science 272:1963–1965

Simon KS, Benfield EF (2001) Leaf and wood breakdown in cave

streams. J North Am Benthol Soc 482:31–39

Simon KS, Pipan T, Culver DC (2007) A conceptual model of the

flow and distribution of organic carbon in caves. J Cave Karst

Stud 69:279–284

Sket B, Paragamian K, Trontelj P (2004) A census of the obligate

subterranean fauna of the Balkan Peninsula. In: Griffiths HI,

Krystufek B, Reed JM (eds) Balkan biodiversity, pattern and

process in the European hotspot. Kluwer, Dordrecht, pp 309–322

Smart C, Worthington SRH (2004a) Groundwater in karst. In: Gunn J

(ed) Encyclopedia of cave and karst science. Fitzroy Dearborn,

New York, pp 394–397

Smart C, Worthington SRH (2004b) Water tracing. In: Gunn J (ed)

Encyclopedia of cave and karst science. Fitzroy Dearborn, New

York, pp 769–771

Smith K, Ward R (1998) Floods—physical processes and human

impacts. Wiley, Chichester, 382 pp

Soulsby C, Tetzlaff D, Rodgers P, Dunn SM, Waldron S (2006)

Runoff processes, stream water residence times and controlling

landscape characteristics in a mesoscale catchment: an initial

evolution. J Hydrol 325:197–221

Tabarosi D (2002) Biokarst on a tropical island. Theor Appl Karstol

15:73–91

Viles HA (1984) Biokarst: review and prospect. Prog Phys Geogr

8:523–548

Vlasceanu L, Popa R, Kinkle B (1997) Characterization of Thiobacil-lus thioparus LV43 and its distribution in a chemoautotrophically

based groundwater ecosystem. App Environ Microbiol 63:3112–

3227

White WB (2002) Karst hydrology: recent developments and open

questions. Eng Geol 65:85–105

Williams PW (1983) The role of subcutaneous zone in karst

hydrology. J Hydrol 61:45–67

WMO (2006) Environmental aspects of integrated flood management.

WMO flood management policy series. WMO-No.1009, Geneva,

71 pp

Worthington SRH (1999) A comprehensive strategy for understand-

ing flow in carbonate aquifers. In: Palmer AN, Palmer MV,

Sasowsky ID (eds) Karst modeling. Karst Waters Institute

Special Publication 5, Charles Town, pp 30–37

Zalewski M, Janauer GS, Jolankai G (eds) (1997) Ecohydrology—a

new paradigm for the sustainable use of aquatic resources. IHP

UNESCO Technical Documents in Hydrology No. 7, Paris, 58

pp

Zalewski M (2002) Ecohydrology the use of ecological and hydro-

logical processes for sustainable management of water resources.

Hydrol Sci J 47(5):823–832

Zambo L (2004) Hydrological and geochemical characteristics of the

epikarst based on field monitoring. In: Jones WK, Culver DC,

Herman JS (eds) Proceedings of the symposium held October 1

through 4, 2003, Shepherdstown, West Virginia, USA, Karst

Waters Institute, Charles Town, pp 135–139

900 Environ Geol (2009) 56:891–900

123