1

Noosa River Loads and Impacts Study

Interim Report

submitted to

WBM Oceanics

by

Ecosystem Health Monitoring Program

Adrian B. Jones BSc (Hons) PhD

Ivan Holland BSc LLB

Courtney Henderson BEnvSc (Hons)

Paul J. Lutz BSc

Dan Wruck BSc

Angela M. Grice BSc (Hons) PhD

William C. Dennison BA MS PhD

June 2001

2

TABLE OF CONTENTS

1. INTRODUCTION 3

2. MATERIALS AND METHODS 6

2.1 Study Sites 6

2.2 Water Column Parameters 8

2.2.1 Total Suspended Solids 8 2.2.2 Nutrients 8 2.2.3 Chlorophyll a 8 2.2.4 Phytoplankton Bioassays 9

2.3 Sediment Parameters 9

2.3.1 Sediment elements 9 2.3.2 Sediment Nutrients 10 2.3.3 Sediment δ15N Isotopic Signature 10

2.4 Plant Parameters 10

2.4.1 Inhabitant Plant delta δ15N values 10 2.4.2 Deployed Macroalgae delta δ15N values 11 2.4.3 Seagrass Depth Range Profiles 11

3. RESULTS & DISCUSSION 12

3.1 Water Column Parameters 12

3.1.1 Total Suspended Solids 13 3.1.2 Dissolved Water Column Nutrients 13 3.1.3 Chlorophyll a 14 3.1.4 Phytoplankton Bioassays 15

3.2 Sediment Parameters 17

3.2.1 Sediment Nutrients 17 3.3 Plant Parameters 17

3.3.1 Inhabitant Plant δ15N isotopic signatures 17 3.3.2 Deployed Macroalgae δ15N isotopic signatures 18 3.3.3 Seagrass Depth Range Profiles 18

3.4 Summary 21

4. REFERENCES 23

3

1. INTRODUCTION

The headwaters and much of the upper Noosa River Catchment is preserved within Cooloola

National Park. It is a largely intact choked coastal lagoon system (Fig. 1), containing a

diverse range of bed and bank habitats, and supports a range of fish species. The Noosa

River catchment covers a total area of approximately 950 km2. The headwaters originate in

the Womalah escarpment and enter the first major tributary, Teewah Creek. The Upper

Noosa River flows south through the low lying Noosa Plain into Lake Cootharaba, where Kin

Kin Creek enters. The Noosa River continues into Lake Cooroiba and into the ocean at

Noosa Heads. Lakes Weyba and Doonella are in the lower reaches of the river (Fig. 1).

Lake Cootharaba

Lake Cooroiba

Lake Doonella

Lake Weyba

BurgessCreek

Kin KinCreek

RingtailCreek

Teewah Creek

Figure 1 Noosa River Catchment boundaries including Kin Kin Creek, Tewah Creek, Ringtail Creek, Lake Cootharaba, Lake Cooroiba,

Lake Doonella, Lake Weyba and Burgess Creek.

4

The riparian zones along most of the river are in relatively good condition, although there has

been extensive clearing in the lower section of the river around the towns of Tewantin,

Noosaville and Noosa Heads. Rural (grazing, horticulture and sugar cane), rural residential,

urban, industrial, State Forest and National Parks are the dominant land uses (Fig. 2 & 3).

The catchment consists of 6 km2 of Sugar Cane and 37.8 km2 of mangroves.

Private Freehold

National Park

State Forest

Crown Land

Figure 2 Land Tenure in the Noosa River Catchment

Natural ConditionRural

Urban

Rural Residential

Highly Impervious

Figure 3 Land Use in the Noosa River Catchment

In contrast to most other rivers in southeast Queensland, the Noosa River does not receive

any sewage inputs. The Noosa Wastewater Treatment Plant discharges into Burgess Creek

south of Noosa, which discharges directly into the Pacific Ocean.

Main inputs to Noosa River are stormwater and catchment runoff. Possible point sources

include acid sulfate soil runoff, land disposal of sewage effluent, industrial runoff (Eenie

Creek catchment), agricultural runoff (Kin Kin catchment), stormwater runoff (urban areas),

canal development runoff, boat waste (olis, grease, sewage), and general litter. Cane farms in

the catchment apply 938 kg of Diuron every year. Clearing of riparian vegetation along Kin

5

Kin Creek results in elevated turbidity in the Noosa River during high flow events.

Consequently increased sedimentation is occurring in the lower lakes and river system.

Urban development is concentrated in the southern sub-catchments and has considerable

impact on the riparian vegetation within the creeks. Mass clearing for housing estates is

widespread in these areas, resulting in greatly increased inputs of sediments and nutrients to

the creeks and river. In some of the urban areas exotic weed invasion is significant and some

species identified such as Brachiaria mutica (Para grass) and Wedelia trilobata (Singapore

daisy) have the ability to dominate the waterways, out-competing the native species.

The majority of rural land use activities (grazing, sugar-cane, small cropping, and fruit and

nut orchards) occur within the Kin Kin Creek, Ringtail Creek, and Cooloothin Creek sub-

catchments. Vegetation in these areas (mostly riparian rainforest) is now restricted to a

narrow fringe along stream banks and consequently is susceptible to disturbance from

grazing, fire and weed invasion. In most grazed areas animals frequent the creek banks for

grazing, resulting in trampling and consumption of vegetation (reducing ability for

regeneration of rainforest species) and development of tracks increasing bank instability and

erosion.

Animals also contribute to the introduction of weeds with some areas dominated by exotics

such as the Camphor Laurel, Chinese Elm, Small Leaved Privet and Lantana. Areas with

very good riparian zones contain significant areas of native hardwood forest, while areas

dominated by exotic pine plantations are typically in very poor condition with a narrow

remnant width.

Boat wash is the major recreational pressure resulting in bank erosion, undercutting and

collapse of fringing vegetation particularly in the region between Lake Cootharaba and Lake

Cooroiba and along the north shore near the town of Noosaville. Popular swimming holes

also suffer from trampling of riparian vegetation from animals, vehicles and human tracks.

The impacts of fertilisers, herbicides and insecticides on golf courses may also impact on the

ecosystem. The quarry at the north west corner of Lake Cooroibah and the industrial area

adjacent to Eenie Creek are the major industrial pressures on the catchment. Acid sulfate

soils appear exposed near the quarry and may result in acidic water entering the lake during

6

rain events. Stormwater from the industrial area has been connected with petrochemical

pollution in Eenie Creek.

The primary aim of this project was to carry out surveys including biological assays and

water column and sediment parameters during wet and dry (high and low flow) periods to

determine the loads and impacts on the Noosa River and to design an appropriate ecological

monitoring program for the region to be incorporated into the expansion of the existing

Ecosystem Health Monitoring Program for Moreton Bay and its River Estuaries.

2. MATERIALS AND METHODS

2.1 Study Sites

Fourteen sites were chosen along the Noosa River including Lake Cootharaba, Lake

Cooroiba and Lake Weyba (Fig. 4). The wet (high flow sampling) at all sites took place on

the 20th and 21st of March, 2001. During sampling on the 21st March, torrential rain resulted

in considerable runoff into the river. Sites were chosen along the river and named according

to AMTD distances upstream. The first site was near the mouth of the river (0.3 km), with

one at 2.3 km. Two sites were chosen in Lake Weyba, W1 (at the entrance to Weyba Creek

with flows into the Noosa River) and W2 midway along the western shore of the lake. Sites

3.9 km, 5.3 km, 6.9 km, and 8.5 km were between Webya Creek and Lake Cooroiba. Site

10.3 km was at the southern end of Lake Cooroiba, 16.0 km and 18.8 km between Lake

Cooroiba and Lake Cootharaba. Site 21.5 km and 26.0 km were in Lake Cootharaba, and site

30.8 at the entrance to Kin Kin Creek.

7

Figure 4 Map of sampling sites in the Noosa River

8

2.2 Water Column Parameters

Salinity (expressed on the Practical Salinity Scale ), pH and dissolved oxygen were measured

with a Horiba U-10 water quality meter (California, U.S.A.).

Secchi depth was used as a measure of water column turbidity, which involves lowering a 30

cm diameter secchi disk (black and white alternating quarters) through the water column until

it is no longer possible to distinguish between the black and white sections.

2.2.1 Total Suspended Solids

Total suspended solids concentrations were determined using the methods of Clesceri et al.

(1989). A known volume of water was filtered onto a pre-weighed and pre-dried (110 ºC; 24

h) Whatman GF/C glass fibre filter. The filter was then oven dried at 60 ºC for 24 h and total

suspended solids calculated by comparing the initial and final weights (Clesceri et al., 1989).

2.2.2 Nutrients

Dissolved inorganic nutrients (NH4+, NO3

-/NO2-, and PO4

3-) were determined by filtering

water samples through Sartorius Minisart 0.45 µm membrane filters and freezing them

immediately. Samples were analysed within two weeks by the NATA accredited Queensland

Health Analytical Services Laboratory in accordance with the methods of Clesceri et al.,

(1989) using a Skalar autoanalyser (Norcross, Georgia, U.S.A.).

2.2.3 Chlorophyll a

Chlorophyll a concentrations were used as an indicator of phytoplankton biomass. At each

site, chlorophyll a concentration was determined by filtering a known volume of water

through a Whatman GF/F filter which was immediately frozen. In the lab, the filter was

ground in acetone to extract chlorophyll a, spectral extinction coefficients were determined

on a spectrophotometer and chlorophyll a concentrations calculated according to Parsons et

al. (1989).

9

2.2.4 Phytoplankton Bioassays

Phytoplankton bioassays were used to determine the response of ambient phytoplankton to

nutrient additions and changes in light intensity. Four litres of site water were filtered through

a 63 µm mesh (to screen out the large zooplankton grazers) into one of 6 sealed transparent

4L plastic containers. Six treatments were established: a control (no nutrient addition),

nitrate (200 µM, NO3-), ammonium (30 µM, NH4

+), phosphate (20 µM, PO43-), urea (5 µM,

urea) and a +All treatment (all nutrients at concentrations mentioned). These concentrations

were used as they are known to be saturating for phytoplankton in estuarine environments.

The bioassay containers were placed in flow-through incubation tanks (2m diameter, 0.5 m

deep) to maintain constant water temperature. To maintain constant irradiance, incubation

tanks were covered with 50% neutral density shade screens. At identical daily circadian

times, all bioassay bags were gently shaken and 20mL from each container was poured into

pre-rinsed 30 ml glass test tubes and placed in darkness for 20 minutes to allow photosystems

to dark adapt. Chlorophyll a concentrations were determined from in vivo fluorescence

(indicating phytoplankton biomass) on a Turner Design Fluorometer. An initial measure

(time = 0) was taken on the control treatment and then for all treatments daily for 7 days.

Over the 7 day period settlement of suspended solids within samples may occur and light

availability increase above ambient levels. The response of the plankton community in the

control bioassay container gives an indication of the ambient light conditions. Light

stimulated phytoplankton bloom potential was calculated as the difference between initial

(time = 0) and maximum in vivo fluorescence values in the control water sample over the 4

day incubation. Nutrient stimulated bloom potential was calculated as the difference between

the maximum response in the nutrient treatments and the maximum response in the control

(referred to as the stimulation factor). This stimulation factor can be used to determine the

relative importance of the different nutrient additions compared with light.

2.3 Sediment Parameters

2.3.1 Sediment elements

Sediments were collected for metal content according to methods adopted for the sediment

nutrients (above). Samples were oven dried and ground to a homogenous powder. Samples

10

were microwave digested in a 1:5:4 mixture of HCl, HNO3 and HF using a CEM MSP 1000

digester. Samples were then analysed by ICP MS scanning for the presence of metals and

other elements (CSIRO Livestock Industries).

2.3.2 Sediment Nutrients

Three replicate samples were collected with 50 mL cut-off syringes, stored in ziplock plastic

bags and stored on ice. Upon return to the laboratory, they were freeze dried and sent to the

NATA accredited, Queensland Health Analytical Services to be analysed using acid digestion

techniques. Subsamples were taken for analysis of organic content in a muffle furnace at 520

°C for 24 h to combust all organic material.

2.3.3 Sediment δ15N Isotopic Signature

Sediment %nitrogen and %carbon content, δ15N and δ13C were determined from three

replicate samples collected with 50 mL cut-off syringes, stored in sterile ziplock bags and

frozen. Samples, were oven dried to constant weight (24 h at 60 °C), ground and two sub-

samples were oxidised in a Roboprep CN Biological Sample Converter (Europa Tracermass,

Crewe, U.K.). The resultant N2 was analysed by a continuous flow isotope ratio mass

spectrometer (Europa Tracermass, Crewe, U.K.). Total %N of the sample was determined,

and the ratio of 15N to 14N was expressed as the relative difference between the sample and a

standard (N2 in air) using the following equation (Peterson & Fry 1987): δ15N = (15N/14N

(sample) / 15N/14N (standard) – 1) x 1000 (‰)

2.4 Plant Parameters

2.4.1 Inhabitant Plant delta δ15N values

There are two naturally occurring forms of nitrogen (N), 14N and 15N with the former being

the most common. The δ15N signature is calculated from the relative amount of 15N to 14N.

Various sources of nitrogen have a specific and measurable δ15N signature. For example,

sewage is enriched with 15N and therefore has a δ15N signature of approximately 10o/oo

(Heaton 1986). Plants uptake the nitrogen source and reflect this δ15N signature. Analysis of

11

their tissue may indicate the nitrogen sources available to the plants. Aquatic plants were

collected and dried at 60oC prior to grinding and analysis. Samples were analysed for δ15N

using a Europa Scientific “Tracermass” continuous flow stable isotope ratio mass

spectrometer with a Europa Scientific “Roboprep” preparation system. Total %N of the

sample was determined, and the ratio of 15N to 14N was expressed as the relative difference

between the sample and a standard (N2 in air) using the following equation (Peterson & Fry,

1987): δ15N = (15N/14N (sample) / 15N/14N (standard) – 1) x 1000 (‰).

2.4.2 Deployed Macroalgae delta δ15N values

The extent of sewage derived nitrogen along the creeks and into the Pacific Ocean was

assessed by the deployment of the macroalga Catenella nipae (sourced from a low nutrient

area) in submerged chambers at half secchi depth to ensure uniform light availability. At

each site, macroalgae are housed in transparent, perforated chambers and suspended in the

water column using a combination of buoy, rope and weights. The algae are be incubated for

4 days to allow nutrient uptake by the algae. Algal samples are oven dried to constant weight

(24 h at 60 °C), ground and two sub-samples are oxidised in a Roboprep CN Biological

Sample Converter (Europa Tracermass, Crewe, U.K.). The resultant N2 is analysed by a

continuous flow isotope ratio mass spectrometer (Europa Tracermass, Crewe, U.K.). Total

%N of the sample was determined, and the ratio of 15N to 14N was expressed as the relative

difference between the sample and a standard (N2 in air) using the following equation

(Peterson & Fry, 1987): δ15N = (15N/14N (sample) / 15N/14N (standard) – 1) x 1000 (‰)

2.4.3 Seagrass Depth Range Profiles

Seagrass depth range is calculated as the vertical distance between a fixed upper marker and

the maximum depth of seagrass survival and is measured with a survey level and staff. To

allow comparison between sites the vertical distance between the fixed upper marker and the

nearest survey mark is calculated. Depth range was calculated at two sites where extensive

seagrass beds were present, in Lake Cooroibah and near Tewantin.

12

3. RESULTS & DISCUSSION

3.1 Water Column Parameters

Secchi depth was relatively constant throughout the length of the Noosa River, excepting the

21.5 km site in Lake Cootharaba which was most likely elevated due to resuspension of

sediment from the lake bottom, due to the shallow nature of the lake.

Table 1 Water quality parameters for Noosa River.

Site Secchi(m) Salinity DO% Turbidity Temp(ºC) pH

0.3 1.4 23.5 102.7 1 28.5 8.10

2.3 1.3 22.2 95.2 2 28.3 8.01

W1 >0.4 23.5 118.9 5 30.8 8.26

W2 nd nd nd nd nd nd

3.9 1.2 19.1 87.4 2 28.0 7.87

5.3 1.1 17.9 86.0 4 27.9 7.79

6.9 1.0 16.3 81.1 3 28.1 7.64

8.5 1.2 16.7 82.7 3 27.5 7.74

10.3 0.9 15.0 91.0 8 27.6 7.70

16.0 1.5 13.9 77.9 3 27.0 7.40

21.5 0.6 12.5 79.8 15 27.9 7.18

26.0 >1.4 14.1 85.2 1 26.4 7.60

30.8 nd nd nd nd

13

3.1.1 Total Suspended Solids

Total Suspended Solids (TSS) within the Noosa River increases upstream to peak at the

shallow regions of Lake Cooroibah and Lake Cootharaba. The concentrations in Lake

Weyba are also higher than all other sites within the rivers. These peaks are likely due to

resuspension of sediments due to the strong winds, shallow water depth and relatively large

fetch which occurs within the lakes (Fig. 5).

0

2

46

8

10

12

1416

18

20

0 5 10 15 20 25

Site (AMTD km Upstream)

To

tal S

usp

end

ed S

olid

s (m

g l-1

)

W1

Figure 5 Total suspended solids concentrations in the Noosa River.

3.1.2 Dissolved Water Column Nutrients

Dissolved inorganic nutrient concentrations (Fig. 6) in the Noosa River are one to two orders

of magnitude lower than many other southeast Queensland rivers. In most of these rivers the

dissolved nutrients are predominantly inorganic, however in the Noosa River, these nutrients

make up a small fraction of the total nutrient concentration, indicating that particulate and / or

dissolved organic nutrients are a major component. Given the relatively low turbidity in the

Noosa River, it is more likely dissolved organic nutrients.

14

0

0.5

1

1.5

2

2.5

3

0 5 10 15 20 25 W1

Site (AMTD km Upstream)

Nu

trie

nt

Co

nc

en

tra

tio

n (

µM

)

NH4+

NO3-

PO43-

Figure 6 Dissolved water column nutrient concentrations for sites in the Noosa River.

0

5

10

15

20

25

30

0 5 10 15 20 25 W1

Site (AMTD km Upstream)

Nu

trie

nt

Co

nce

ntr

atio

n (

µM

)

NP

Figure 7 Total water column nutrient concentrations for sites in the Noosa River.

3.1.3 Chlorophyll a

Chlorophyll a is fairly constant along the length of the river, excepting the mouth of the river

and the mouth of Kin Kin Creek, which corresponds to the regions of lowest dissolved

nutrient concentrations (Fig. 8). The highest chlorophyll a concentration was in Lake Weyba

at site W1.

15

0

0.5

1

1.5

2

2.5

3

3.5

4

0 5 10 15 20 25 W1

Site (AMTD km Upstream)

Ch

loro

ph

yll a

(µg

l-1)

Figure 8 Chlorophyll a concentrations for sites in the Noosa River.

3.1.4 Phytoplankton Bioassays

Phytoplankton communities in the upper reaches of the Noosa River and in Lake Weyba

respond to additions of urea suggesting an adaptation to organic forms of nitrogen. At all

other sites the phytoplankton community was co-limited by nitrogen and phosphorus. The

greatest potential for phytoplankton blooms is at the mid river sites (5.3 km to 10.3 km

AMTD) (Fig. 9).

16

W1

0

10

20

30

40

50

0 1 2 3 4 5 6 7Days

Flu

ore

sc

en

ce

0.3 Km

0

20

40

60

80

100

0 1 2 3 4 5 6 7Days

Flu

ore

sc

en

ce

2.3 Km

01020304050607080

0 1 2 3 4 5 6 7days

flu

ore

sc

en

ce

3.8 Km

0

10

20

30

40

5060

70

0 1 2 3 4 5 6 7Days

Flu

ore

sc

en

ce

5.3 Km

0

50

100

150

200

250

300

350

0 1 2 3 4 5 6 7Days

Flu

ore

sc

en

ce

6.9 Km

0

50

100

150

200

0 1 2 3 4 5 6 7Days

Flu

ore

sc

en

ce

8.5 Km

020406080

100120140160180200

0 1 2 3 4 5 6 7Time

Flu

ore

sc

en

ce

10.3 Km

0

20

40

60

80

100

120

140

160

0 1 2 3 4 5 6 7Time

Flu

ore

sc

en

ce

16.0 Km

0

10

20

30

40

50

60

0 1 2 3 4 5 6 7Time

Flu

ore

sc

en

ce

21.5 Km

0

20

40

60

80

100

120

0 1 2 3 4 5 6 7Time

Flu

ore

sc

en

ce

26.0 Km

05

10152025303540

0 1 2 3 4 5 6 7Time

Flu

ore

sc

en

ce

control

NO3

NH4

PO4

Urea

All

Figure 9 Phytoplankton Bioassay responses for sites in the Noosa River.

17

3.2 Sediment Parameters

3.2.1 Sediment Nutrients

The concentration of total nitrogen in the sediment was highest at the 16.0 km site located

between Lake Cooroibah and Lake Cootharaba and at site 8.5 km between Tewantin and

Lake Cooroibah. Site 16.0 corresponds to the region where Cooloothin and Ringtail Creeks,

which drain the regions with the majority of rural land use activities (Burrows, 1998). All

sites upstream and downstream of these (and the site in Lake Cooroibah) were significantly

lower. In Lake Weyba site W2 was significantly higher than W1, which may correlate to the

presence of a stormwater drain near site W2. The concentration of total phosphorus is an

order of magnitude lower than total N, but follows similar trends in concentrations between

sites (Fig. 10).

0

500

1000

1500

2000

2500

0 5 10 15 20 25 30 35 W1 W2Site (AMTD km Upstream)

Nu

trie

nt

Co

nc

en

tra

tio

n (

mg

kg

-1)

NP

Figure 10 Sediment total nitrogen and total phosphorus concentrations for sites in the Noosa River.

3.3 Plant Parameters

3.3.1 Inhabitant Plant δ15N isotopic signatures

Stable isotope ratios of nitrogen (δ15N) have been used widely in marine systems as tracers of

discharged nitrogen from point and diffuse sources, including sewage effluent (Rau et al.,

1981; Heaton, 1986; Wada et al., 1987; Van Dover et al., 1992; Macko & Ostrom, 1994;

Cifuentes et al., 1996; McClelland & Valiela, 1998). Plant δ15N signatures have been used to

18

identify nitrogen sources available for plant uptake (Heaton, 1986). Elevated δ15N signatures

in aquatic flora have been attributed to assimilation of N from treated sewage effluent (Wada

et al., 1987; Grice et al., 1996; Udy & Dennison, 1997; Abal et al., 1998). The presence of

sewage derived nitrogen was determined by analysing the δ15N signature of aquatic flora at

all sites.

Results not yet available

Figure 11 δ15N concentrations of inhabitant macrophytes for sites in the Noosa River.

3.3.2 Deployed Macroalgae δ15N isotopic signatures

Results not yet available

Figure 12 δ15N concentrations of deployed macroalgae for sites in the Noosa River.

3.3.3 Seagrass Depth Range Profiles

The relationship between seagrass depth range (SDR) and light availability provides the

ability to integrate the impacts of improved or reduced water clarity. Seagrass will grow to a

depth where they are receiving the minimum light requirements for survival. The correlation

between seagrass depth range and water quality (nutrients, chlorophyll a and suspended

solids) was determined in Moreton Bay (Abal & Dennison, 1996).

The seagrass depth range at Lake Cooroibah is less than at Tewantin and correlates to the

higher water column turbidity and therefore lower light availability at Lake Cooroibah.

19

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

Tewantin Lake Cooroibah

Site

Sea

gra

ss D

epth

Ran

ge

(m)

Figure 13 Seagrass depth range in Lake Cooroibah Tewantin sites in the Noosa River.

-1.4

-1.2

-1

-0.8

-0.6

-0.4

-0.2

0

0.00 10.00 20.00 30.00 40.00 50.00 60.00 70.00 80.00

Distance (m)

Rel

ativ

e H

eig

ht (

m)

TBM

base of stake in front of mangroves

start Zostera

end Zostera

Figure 14 Seagrass distribution profile in Lake Cooroibah.

20

-2.50

-2.00

-1.50

-1.00

-0.50

0.00

0 2 4 6 8 10 12

Distance (m)

Rel

ativ

e H

eig

ht

(m)

TBM

base of bank

start Zostera

end Zostera

Zostera leaves 40cm30% cover

Figure 15 Seagrass distribution profile in the Noosa River at Tewantin.

21

3.4 Summary

The Noosa River system typically has much lower turbidity, chlorophyll a, and water column

nutrients than other rivers in southeast Queensland. Its nutrients are predominantly organic in

contrast to inorganic in rivers receiving sewage inputs. Turbidity is controlled more by

resuspension of sediments within the lakes than terrestrial inputs or tidal energy, even during

high flow periods (this sampling period) (Plate 1).

Plate 1 Elevated turbidity from runoff during high flow period.

During the wet season, the greatest potential for phytoplankton blooms is in the lower reaches

of the river near Tewantin. Most sites were stimulated by combined additions of inorganic

nitrogen and phosphorus, but responses to organic nitrogen (urea) were observed at upper

reaches of the estuarine section of the river and also in Lake Weyba.

Analysis of δ15N isotopic signatures of inhabitant vegetation and deployed macroalgae may

highlight discharges of septic from unsewered areas within the catchment.

22

Results from the dry sampling trip will help to identify the importance of flushing within the

system and the potential increase or decrease in nutrients contained within the system. The

dry sampling was also conducted during late autumn compared to Summer for the wet

sampling, which may have implications regarding sediment bacterial processing and

biological uptake of nutrients and the magnitude of phytoplankton nutrient responses.

23

4. REFERENCES

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District Landcare Group Inc.

Cifuentes, L.A., Fogel, M.L., Pennock, J.R. & Sharp, J.H. (1989) Seasonal variations in the

stable isotope ratio of ammonium in the Delaware estuary. Geochim Cosmochim Acta

53, 2713-2721.

Clesceri L. S., Greenberg A. E. & Trussel R. R. (1989) Standard methods for the examination

of water and wastewater. American Public Health Association, New York.

Costanzo S. D., O'Donohue M. J., Dennison W. C., Loneragan N. R. & Thomas M. (2001) A

new approach for detecting and mapping sewage impacts. Marine Pollution Bulletin

42: 149-156.

Grice, A.M., Loneragan, N.R. & Dennison, W.C. (1996) Light intensity and the interactions

between physiology, morphology and stable isotope ratios in five species of seagrass.

Journal of Experimental Marine Biology and Ecology 195, 91-110.

Heaton T. H. E. (1986) Isotope studies of nitrogen pollution in the hydrosphere and

atmosphere: A review. Chemical Geology 59: 87-102.

Jones A. B., Dudley B. J. & Dennison W. C. (1998) Factors limiting phytoplankton biomass

in the Brisbane River and Moreton Bay. In: Moreton Bay and Catchment (eds. I. R.

Tibbets, N. J. Hall & W. C. Dennison) pp. 179-186. School of Marine Science, The

University of Queensland, Brisbane.

MacIntyre H. L. & Cullen J. J. (1995) Fine-scale vertical resolution of chlorophyll and

photosynthetic parameters in shallow-water benthos. Marine Ecology Progress Series

122: 227-237.

MacIntyre H. L., Geider R. J. & Miller D. C. (1996) Microphytobenthos: The ecological role

of the secret garden of unvegetated, shallow-water marine habitat. I. Distribution,

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