environmental stresses and intertidal assemblages on hard substrates in the port of long beach,...

Marine Biology 63, 197-211 (1981) MARINE BIOLOGY �9 Springer-Verlag 1981

Environmental Stresses and Intertidal Assemblages on Hard Substrates in the Port of Long Beach, California, USA

Tran-ngoc Loi*

Marine Biological Consultants Inc.; 947 Newhall Street, Costa Mesa, California 92627, USA

Abstract Introduction

Nine intertidal stations within the Port of Long Beach, California, USA, were sampled during September and October 1975 using the random point method and the scraping technique. A total of 96,168 individuals belonging to 55 taxa were recorded in the quantitative survey; qualitative scrapings included 136 taxa. The protected outer coast intertidal assemblages were found at all but three stations along the shorelhae. The shoreline, being situated in between the more environmentally stressed inner harbor and the less stressed open ocean, supported assemblages characterized by an instability in species composition. The upper midlittoral zone was typically dominated by Chthamalus dalli, C fissus and Balanus glandula. The lower midlittoral was colonized either by Antho- pleura elegantissirna-Prionotis lanceolata facies along the outer breakwater or by A. elegantissima-Tetraclita squamosa rubescens facies along the inner breakwater. The mussel bed, which is the characteristic assemblage of the Californian lower midlittoral zone was obscured by the competitors P. lanceolata, T. squamosa rubescens and A. elegantissima, and was thinned out by predators, of which Pisaster ochraceus was the most voracious. Suspension feeders were dominant in the upper midlittoral and producers and grazers in the lower midiittoral. Predators were few in number and restricted to levels below mean lower low water. There was a gradual increase in numbers of intertidal species and individual abundance from level +5 ft (1.5 m) to level +1 ft (0.3 m) and from shoreline to outer breakwater. This may be attributable to the decrease in environmental stresses in the lower water levels and the improvement in water quality from the inner to outer harbor area.

*Present address: The Philadelphia, Nineteenth Pennsylvania 19103, USA

Academy of Natural Sciences of and The Parkway, Philadelphia,

Marine plants and animals which inhabit the environment affected by rhythmic tidal movements are distrib- uted according to their differing abilities to endure exposure to both aerial and marine conditions (tempera- ture, salinity, humidity, surf, etc.). On rocky shores these organisms occupy distinctive zones. Within these zones, interspecific competition (for space, food, etc.) occurs and ultimately structures the assemblage. In this sense, intertidal assemblages are relatively stable in time and space.

The stability of the assemblage is a result of individual species adaptation to physical and biological factors of the environment. Assemblage stability does not necessarily imply that all members of the assemblage are present year-round but, rather, that seasonal fluctuations of populations within the assemblage do not affect the entity of the assemblages and are relatively predictable. When the major components of an assemblage and their interactions have been defmed, the effects of a perturba- tion (both natural and man-induced) on the assemblage can be accurately assessed.

The present study sought to characterize the intertidal assemblages inhabiting the hard substrates of the Port of Long Beach, California and to determine pollution effects, if any, on these assemblages.

Materials and Methods

Study Area

This study was carried out in September and October 1975 at the Port of Long Beach, which is situated in the San Pedro Bay, Los Angeles County, California, USA (Fig. 1). Within this area, 9 intertidal stations on rock embankments with transects extending from the + 5 to 0 ft (1.5 to 0 m) mean lower low water (MLLW) levels were chosen. Stations 11A, 13A and 23 were located on

0025-3162/81/0063/0197/$ 03.00

198 Tran-ngoc Loi: Environmental Stresses and Intertidal Assemblages

11A ................... 13A ~ ~~23 1 8 m ....- - - .

..v" ," O U T E I q ' " H A R B O R

,. )

o Z - ' 57A �9

..... "'" ~ 22B ..... "'"

65B SAN PEDRO BAY

B r e a k w a t e r

H O 1500m Fig. 1. Map of Long Beach

Port, California, showing 9 intertidal stations used in study

the shoreline of Long Beach Harbor; l l A and 13A on the Navy Mole and 23 on Pier J. Paired stations 65A, 65B, 57A, 57B and 22A, 22B lay on the middle breakwater; the A stations on the inner side, the B stations on the outer side.

These 9 stations were all situated on hard substrates consisting mainly of concrete, conglomerate and large granitic boulders with rough and uneven surfaces.

Surface water temperatures taken in Long Beach outer harbor resulted in a mean varying between 13.6 ~ in January and 20.5 ~ in September; the annual thermal range was 6.9 C ~ (Environmental Quality Analysts Inc. and Marine Biological Consultants Inc., 1975).

Surface salinity distribution was quite uniform throughout the year, except for the winter months when rainfall and subsequent terrestrial runoff reduced salinity. High values were observed during April-November as a result of evaporation due to solar warming and of the exchange of bay water with the open ocean. Data collected in the outer harbor exhibited a maximum of 33.65~176 S in June and a minimum of 23.53~ in December (Environmental Quality Analysts Inc. and Marine Biological Consultants Inc., 1975).

Precise tidal data were not available for Long Beach Harbor, but data for the nearby Los Angeles Harbor indicated a semi-diurnal type and a mean range of 2.29 m which is typical of Southern California.

Local wave conditions have not been accurately evaluated. Subjective field observations suggested that strong winds generate wind waves of at least 0.6 to 1 m in height. In addition, an almost unceasing swell of variable height and period strikes the coast from the south, southwest and west in summer and autumn and from the north and northwest in winter. In rough weather and heavy swell conditions the breakwater, 4.27 m above MLLW, would be completely covered with white foam. The three stations 65B, 57B and 22B facing the open Pacific were strongly affected by such water movements.

Sampling Method

Because many intertidal species are diminutive and often exist in densely aggregated colonies, a method known as the random-point contact was used to estimate the percent cover &intertidal organisms within randomly located quadrats. The random method was originally developed for and is commonly applied to vegetation analysis. Goodall (1952) and Grieg-Smith (1964) have provided valuable critical reviews of this method and have supported its application based on efficiency and accuracy.

Tran-ngoc Loi: Environmental Stresses and Intertidal Assemblages 199

~kBenchmork Control

W/lllk\ ":4,~ -,.; Hand ,eve, ,~" +5:4 ?~.<-

/,~.- l~'A"~) 8 Random Q u a d r a t s a l o n g 1 "==~r l / - - ~ ' ~

e 5o o L,n re ,ranaeot '"C" "A" .4' "~":=J-~

, ,~ ' / / / / / / / / =--=.,

- ~ : ~0 Random Point. within Q~adt~t~ ~ ' / Fig. 2. Diagram of random-point contact procedure

Since no benchmarks were present at the stations to derive absolute tidal heights, the distance above MLLW was calculated for each station and survey date from data and methods given in the National Oceanic and Atmospheric Administration Tide Tables for 1975 (Tide Tables, 1975).

The surveys were conducted by 2 or 3 two-man teams, each team at a separate station, during a low tide. A 50 m tape was anchored at the transect and extended along the shoreline parallel to the water's edge. Using a hand level and staff, the exact elevation along the horizontal metered line was obtained by backsighting to a target of known elevation on the transect (Fig. 2). Eight random 0.125 m 2 quadrats along this 50 m horizontal transect were marked off for random sampling. The exact positioning of the quadrat was sub- ject to natural variation in the terrain; small adjustments in position were made to accommodate rock crevices, angle of slope and inappropriate substrate (wood and metal debris). Within each quadrat, 40 random points were sampled and species observed were recorded. Points within the quadrat were located on X, Y co- ordinates measured along the margins of the quadrat.

Exposure, type of substrate and the angle of slope of the quadrat were evaluated at each sampling site. The amount of silt and oil present was also estimated, based upon a field working scale: 1 = none; 2 = light; 3 = medium; 4 = heavy.

At all but two of the stations the random-point contact method couldnot be used at the 0 level (Stations 11A and 23). Although the lowest point of the tide was below 0 level, tidal surge and wave action during the sampling period kept this level covered for the majority of its supposed exposure time. The procedure used for the qualitative study involved collection of a 0.125 m 2 scraping from a typical area close to the beginning of the 50 m transect. These rock scrapings were returned to the laboratory, sorted and identified. Additionally,

7 randomly selected quadrats along the transect were visually examined, all macroorganisms present listed, and an apparent areal dominant designated.

Statistical Analysis

Samples were characterized by the total number of species (S), the total number of individuals (A), and a species diversity index (H'). The Shannon-Wiener index (H') (Shannon and Weaver, 1963) was calculated as H'

s = - ~ p i ( l o g 2 p i ) , where Pi = the proportion of the

i= 1 total number of individuals belonging to the ith species (Pielou, 1966). Evenness was calculated a s f = H'/log2 (S). Species richness was defined as the number of species found in a sample. A group averaging technique (Southwood, 1966) was used to group stations which were similar in species composition; linkage was based on Czekanowski or SCrensen similarity coefficient (Czekanowski, 1909; SCrensen, 1948) Cz = 2 W / ( A + B ) ,

where A = the number of species in Sample a, B = the number of species in Sample b, and W = the number of species present in the two samples being compared (see also Day e t al . , 1971 ; Field, 1971).

Sampling protocol was designed to generate survey data arranged in a manner suitable for classical analyses of variance (ANOVA) applications. The assumption was made that there was no significant interaction between treatments. After examination of the present results, this assumption, though possibly invalid, would not affect my conclusions.

Results

A total of 96,168 individuals belonging to 55 taxa were collected in the quantitative portion of the study


Table 1. List of taxa coUected in September-October 1975 within Port of Long Beach, at +5, 4, 3, 2, and 1 ft (1.5, 1.2, 0.9, 0.6, and 0.3 m) levels using random-point method. Mean abundance among stations, grand mean and rank are also given

Taxa Stations Grand Rank 11A 13A 23 65A 57A 22A 65B 57B 22B mean

Bacillariophyta Unidentified 0 0 0 0 0 0 0 0 0.2 0.02 45

Chlorophyta Unidentified 0 0 34.2 26.2 0 9.4 0.2 0 1.2 7.90 7

Chlorophyceae Chaetomorpha spp. 0 0 0 0 0 0 0 0 0.2 0.02 45 Ulva spp. 42.8 0 0 0.4 8.6 4.0 6.2 4.8 6,8 8.17 6

Phaeophyta Unidentified 0 0.2 30.6 69.8 35.0 6.2 5.0 0.8 0.2 16.41 5

Phaeophyceae Egregia menziesii 6.8 0 0 0 0 0 0 0 0 0.76 19

Rhodophyta Unidentified 0 0 0 0 0 0.2 0.4 0 0 0.07 36

Florideophyceae Acrosorium uncinatum 0 0 0 0 0 0 2.2 0 0 0.24 27 Ceramium spp. 0 0 0 0 0 0 13.4 13.0 0 2,93 13 Corallina spp. 0 2.0 0.2 2.2 16.6 8.4 24.4 2.0 10.0 7.31 8 Gelidium pusillum 0 4 0 6.8 1.0 0.8 0 0 0.2 1.42 18 Gelidium sp. 0 0 0 0 0 0 0 0 0.2 0.02 45 Gigartina papillat~ 0 0 0 0 0.2 0 0 0.2 18.2 2.07 16 Gigartina leptorhynchos 0 0 0 0 20.0 14.0 0.4 0 0 3.82 11 Gigartina spinosa 3 0 0 0 0 0 1.6 0 0 0.51 24 Grateloupia doryphora 0 0 0 0 0 0 0 0 0.2 0.02 45 Nemalion helminthoides 0 0 0 0 0 0 0.2 0.6 0 0.09 34 Prionitis lanceolata 0 0 0 0 0 0 38.0 0 0 4.22 10 Rhodoglossum affine 0 0 0 0 1.2 1.8 1,6 3.0 10.8 2.04 17 Tenarea ascripticia 0 0 0 0 0 0 0 0.2 0 0.02 45

Porifera Unidentified 0 0 0 0 0.2 0 0 0 0 0.02 45

Coelenterata Anthozoa

Anthopleura elegantissima 9.6 7.6 0 12.6 83.6 34.2 44.4 54.4 27.4 30.42 2 Anthopleura xanthogramrnica 0 0 6.8 0 0 0 0 0 0 0.75 21

Ectoprocta Unidentified 0 0 0 0 0.4 0 0 0 0 0.04 41 Bugula neritina 0 0.6 0 0 0 0 0 0 0 0.07 36 Thalamoporella spp. 0 0 0 0 0.2 0.4 0 0 0 0.07 36 Watersipora arcuata 0.5 0 0 0 0 0 0 0 0 0.06 39

Mollusca Polyplacophora

Nuttallina californica 0 0 0 0 0 0 0 0.2 0.2 0.04 41

Gastropoda Acanthina spirata 0 0 0.3 0 0 0 0 0 0 0.03 44 Acmaea sp. 1.2 0.6 3.7 0.6 0 0 0.4 0 0.4 0.76 19 Collisella digitalis 6 0.2 2.8 0 0 0.4 2.6 2.2 6.2 2.26 14 Collisella limatula 0 0.4 0.2 0 0 0.2 0 0 0.2 0.11 33 Collisella ochracea 0.3 0.4 0 0 0 0 0.6 0.2 0 O. 17 31 Collisella scabra 1.8 7.6 5.0 5,8 1,2 9.4 7.4 6.4 5.6 5.57 9 Collisella strigatella 0 0 0 0 0 0 0 0.2 0 0.02 45 Collisella sp. 0.2 0 0 0 0 0 0 0 0 0.02 45 Haliotis cracherodii 0 0 0 0 0 0 1.2 0 0 0.13 32 Lottia gigantea 0 0 0 0 0 0 0.8 0.2 0.6 0.18 30 Littorina planaxis 0 0 1.8 0 0 0 0 0 0 0.20 29 Littorina scutulata 0.2 0.2 0 0 0 0 0 0 0 0.04 41

B~aMa Mytilus californianus 0 0 0 0 0 0 0 0.4 6.2 0.73 22 Mytilus edulis 29 0 0.2 0 0 0 0.8 0 0 3.24 12

Tran-ngoc Loi: Environmental Stresses and Intertidal Assemblages

Table 1 (continued)

201

Taxa Stations

11A 13A 23 65A 57A 22A 65B 57B 22B

Grand mean

Rank

Annelida Polychaeta

Hydroides sp. 0.5 0 0 0 0 0 0 0 0 0.06 39 Serpulidae, unidentified 0 0 0.5 0.2 0 0 0 0 0 0.08 35

Arthropoda Crustacea

Cixripedia Balanusglandula 62.8 22.4 24.2 0.4 1.0 11.2 7.6 10.2 28.4 18.68 3 Chthamalus spp. 15.8 48.8 61.6 45.2 6.4 43.6 21.6 49.0 41.8 37.08 1 Pollicipes polyrnerus 0 0 0 0 0 0 0 0 3.6 0.40 26 Tetraclita squamosa

rubescens 0.8 5.2 39.6 44.2 11.6 6.6 12.4 18.2 11.2 16.64 4 Unidentified 5.0 0.2 0 0.6 1.4 3.8 3.2 0.6 4.8 2.18 15

Malacostraca Gammaridea, unidentified 0 0 0 0 0.2 0 0 0 0 0.02 45

Echinodermata Asteroidea

Patiria rniniata 0 0 0 2.2 0 0 0 0 0 0.24 27 Pisaster oehraceus 0 0 1.2 0.8 0.2 0.2 2.0 1.0 0.4 0.64 23

Echinoidea Stro ngy locentrotus

purpuratus 0 0 4.2 0 0 0 0 0 0 0.47 25

Chordata Urochordata

Ascidiacea Sp. A 0 0 0 0 0.2 0 0 0 0 0.02 45 Sp. B 0 0 0 0 0 0.2 0 0 0 0.02 45

Table 2. List of taxa collected in September-October 1975 within Port of Long Beach, at 0 ft (0 m) level, using scraping technique. Stations l l A and 23, where random-point contact method was used, are not included herein, x indicates presence

Taxa Stations

13A 65A 57A 22A 65B 57B 22B

Porifera Calcispongiae

Leuconia heathi

Demospongiae Halichondria panicea Haliclona permollis Hymeniacidon sinapium Leucetta losangelensis Lissodendoryx noxiosa Plocamia A Plocamia B Syncon coronatum

Coelenterata Anthozoa

Anthopleura elegantissima

Platyhelminthes Unidentified

Rhynchocoela Unidentified

X X

X X X

X X

X X

X X X X X

X X

X X X X X

Continued on page 202

202

Table 2 (continued)


Taxa Stations

13A 65A 57A 22A 65B 57B 22B

Aschelminthes Unidentified

Ectoprocta Gymnolaemata

Cheilostomata Bugula neritina x Costazia sp. x x Hippothoa hyalina x Holoporella brunnea x Membranipora tuberculata x Membranipora sp. Scruparia ambigua x x Thalamoporella ealifornica x

Cyclostomata Crisia occidental& x Crisia sp. x Crisulipora occidentalis x Filicrisia geniculata x Filicrisia sp. x x

Mollusca Polyplacophora

Chaetopleura gemma Unidentified

Gastropoda Prosobranchia

A eanthina spirata Acmaea insessa A cmaea spp. Barleeia californica Barleeia haliotiphila Crepidula onyx Epitonium tinctum Lacuna unifasciata Megatebennus bimaculatus Mitrella sp. Oeenebra poulsoni Sinezona rimuloides Urosalpinx circumtexta

Opisthobranchia Aegires albopunctatus Tenellia ?ventilabrum ?Trinchesia sp.

Bivalvia Chama pellucida Gregariella coralliophaga Hiatella aretica Kellia laperousi Lasaea adansoni subviridis Modiolus capax Modiolus rectus Mytilus edulis Philobrya setosa Protothaea sp. Rupellaria carditoides Rupellaria tellimyalis

Annelida Polychaeta

Arabella irieolor Arabella pectinata Autolytus (Regulatus) kiiensis Boccardia proboscidea Capitellidae, unidentified

X X

X

X

X

X

X

X

X X

X X

X


Table 2 (continued)

203

Taxa Stations

13A 65A 57A 22A 65B 57B 22B

Chone ecaudata Chone sp. Chone veleronis Cirratulidae, unidentified Dodecaceria concharum Eulalia quadrioculata Eumida bifoliata Eupomatus graeilis Exogone lourei Halosydna brevisetosa Halosydna /ohnsoni Haplosyllis spongicola Lepidonotus sp. Nainereis dendritica Nereis mediator Nereis sp. Paleanotus bellis Platynereis bicanalieulata Phylloehaetopterus prolifica Polydora limicola Polyophthalmus pictus Typosyllis aciculata Typosyllis fasciata

Sipunculida Phascolosoma agassizff

Arthropoda Pycnogonida

Ammothella setosa Lecythorhynchus hilgendorfi Unidentified

Crustacea Ostracoda

Bairdiidae, unidentified Cythereis sp. A Cythereis sp. B Unidentified

Copepoda Unidentified

Cirripedia Balanus tintinnabulum Chthamalus dalli Chthamalus fissus Tetraclita squamosa rubescens

Malacostraca Ampithoe spp. Anatanais normani Aoroides columbiae Cancer antennarius Caprella brevirostris Caprella penantis Caprella sp. Caprella verrueosa Corophium acherusicum Corophium sp. Cumacea, unidentified Elasmopus rapax Elasmopus sp. Gammaridae, unidentified Gammaropsis thompsoni Hemigrapsus sp. Hyale frequens Hyale sp. Ianiropsis tridens

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X X X

X X

X X X

X

X

X

X

X

Continued on page 204

204

T a b l e 2 (continued)


Taxa Stations

13A 65A 57A 22A 65B 57B 22B

Jaeropsis dubia Jassa falcata x x Leptochelia sp. Leucothoe alata Munna sp. Pachycheles rudis Pachygrapsus crassipes Photis sp. x Podocerus brasiliensis x Pugettia gracilis Pugettia producta x Sphaeroma pentodon x Stenothoe sp. x Synapseudes intumescens

Echinodermata Asteroidea

Pisaster ochraceus x

Echinoidea Strongylocentrotus purpuratus x

Holothuroidea Eupentacta quinquesemita Unidentified x

Ophiuroidea Ophiactis sp. x x

Chordata Urochordata

Aseidiacea Unidentified x

X X

X

X X X

X X

40

m 30 "o m g | Q,

2O c

~ 10 o o

- - 0

x 3 0

13

TIDAL LEVELS Iinftl 4 5

0 l t A 13A 23 B5A 57A 2 2 A 6 5 B 5 7 B 2 2 B

Shorel ine Inner Breakwater Outer Breakwater S T A T I O N S

Fig. 3. Mean number of taxa per 40 contact points per quadrat at various tidal levels and intertidal stations. Tidal levels were 1 ft (0.3 m) intervals from 0 (meanlower low water) to +5 ft (1.5 m)


cr

o.

p,

m

oo o

r

Q

Q Z

u. O

,,=,

z

4 0

3 0

20

, o 1 o M

3 4 5 T I D A L L E V E L S [in ftl

3O

11A 13A 2 3 6 5 A 57A 2 2 A 6 5 B 57B 22B Shoreline Inner Breakwater Outer Breakwate r

S T A T I O N S

Fig. 4. Mean number of individuals per 40 contact points per quadrat at various tidal levels and intertidal stations. Tidal levels were at 1 ft intervals from 0 (mean lower low water) to +5 ft

Table 3. Analysis of variance of mean number of taxa and mean number of individuals in area studied

Source of variation DF Mean square F

Mean no. of taxa Level 4 122.13 56.76* Station 6 12.40 5.76* Residual 349 2.152

Total 359

Mean no. of individuals Level 4 9438.47 92.11" Station 6 1162.28 1!.34" Residual 349 102.47

Total 359

*P <~ 0.001

the mean number of taxa (Table 3) indicates highly significant differences among levels and stations. The mean number of taxa increased from level + 5 ft (11 taxa) down to level + 1 ft (40 taxa). At level 0, analysis of the scrapings revealed 136 taxa; only 9 of these were encountered at the other five levels. This difference in number of taxa is attributable to small and/or cryptic epibionts associated with the algal turf and/or the mussel bed; these habitats provide not only food but protection from desiccation because they retain mois- ture at ebb tide. The mean number of taxa increased, on the other hand, from the western stations to the eastern stations and from the shoreline stations to the outer breakwater stations. Stations l l A and 13A on the Navy Mole had the lowest mean number o f taxa (15 taxa); Station 22B on the outer breakwater had the highest mean number of taxa (25 taxa).

(Table 1). The qualitative scrapings contained 136 taxa (Table 2), only 9 of which were recorded in the quantitative survey.

Number of Taxa

Fig. 3 presents the mean number of taxa as a function of tidal level (0 to +5ft) and station (arranged from west to east and shoreline to outer breakwater). An ANOVA of

Number of Individuals

Like the mean number of taxa, the mean number of individuals also increased from level +5 ft down to level + 1 ft and exhibited significant differences among levels and stations (Fig. 4 and Table 3). The greatest and smallest abundances were found at Stations 23 and 13A, respectively. The great abundance at Station 23 was due to the heavy cover of unidentified Chlorophyta and Phaeophyta. Low abundance at Station 13A was associated with the lack of these microscopic algae.

206

2 . 0


0 , 4

1.5

1.0

-- 0.5 z w

)-

bd

m r, 3 .5

Cn MI

O al L u) 3 .0

2 .5

2 .0

T IDAL L E V E L S [in f t l

1 . 5

../.. /

i , i i , ,

. A I~A 2'3 11sA 5rA 22A 11Se 5~B 22B Shoreline I n n e r B r e a k w a t e r Outer Breakwater

STATIONS

Fig. 5. Shannon-Wiener diversity indices (H') of intertidal associations at various tidal levels and intertidal stations. Tidal levels were at 1 ft intervals from 0 (mean lower low water) to +5f t

Data for the mean number of individuals at level 0 were not used in Fig. 4 because of the previously men- tioned non-quantitative nature of the collection. Stations l l A and 23, for which quantitative 0 level information was obtained, had mean abundances of 32 and 38 individuals per replicate, respectively. Subjective field observations suggested that overall 0 level abundance was lower than +1 ft level abundance. This difference was apparently due to intensive sea urchin gazing and high concentrations of predators. Algal turf may have also contributed to the exclusion of various larger animals.

Species Diversity and Evenness

The mean species diversity (H') for each level (except 0) and station is presented in Fig. 5). Species diversity was significantly different among levels and stations. It gradually decreased in value from level + 1 ft to level

0.3

0.2

0.1

Z

Z 0.8 Iu > ul

0 , 7

0 . 6

0 . 5

O

i . . i i

1 2 3 4 5 T IDAL LEVELS [ i n f t ]

" \ / \ / 'J

i i i i , , , , i

11A 13A 23 65A 57A 22A 6511 5711 22B S h o r e l i n e I n n e r Breakwater Outer B r e a k w a t e r

STATIONS

Fig. 6. Evenness coefficients (J') of intertidal associations at various tidal levels and intertidal stations. Tidal levels were at 1 ft intervals from 0 (mean lower low water) to +5 ft

+5 ft, where there were only a few limpets and littorinid snails and Chthamalus spp. The diversity at level + 1 ft was a little lower than that at level +2 ft; subjective field observations suggested an even lower value at level 0. Stations 65A and 22A achieved the highest diversities because of their great abundances of algae, molluscs and barnacles.

The mean species evenness (J ' ) exhibited patterns similar to those of the mean species diversity (Fig. 6).

Dominance

Not all species in an assemblage are equally important. Out of hundreds of species present in an assemblage, relatively few are successful in exerting a controlling influence over the occurrence of other species; these few are the dominant species. Dominance is often closely related to abundance, for a numerically abundant species usually determines the nature of the assemblage. Nevertheless, in some cases, a rare species, e.g. an active predator, may be dominant because of its impact on more numerous cohabitants (P6r6s and Picard, 1964; Paine, 1966).

Analysis of the 55 taxa encountered in the quantitative survey showed a marked dominance of algae (19 taxa) and molluscs (17 taxa); the barnacles ranked third (5 taxa). Distribution by feeding type for these


Table 4. Fourteen dominant taxa taken in September-October 1975 within Port of Long Beach. Mean abundance among levels and stations, grand mean and rank are also given

Taxa Mean abundance Grand Rank mean

Levels Stations

1 2 3 4 5 l lA 13A 23 65A 57A 22A 65B 57B 22B

Chthamalusspp. 15.77 23.88 41.55 70.00 34.22 15.8 48.8 61.6 45.2 6.4 43.6 21.6 49.0 41.8 37.08 1 Anthopleura elegantissima 61.33 54.44 32.22 4.11 0 9.6 7.6 0 12.6 83.6 34.2 44.4 54.4 27.4 30.42 2 Balanusglandula 5.88 13.11 42.66 30.33 1.44 62.8 22.4 24.2 0.4 1.0 11.2 7.6 10.2 28.4 18.68 3 Tetraclitasquamosarubescens 28.77 32.11 14.66 6.11 1.55 0.8 5.2 39.6 44.2 11.6 6.6 12.4 18.2 11.2 16.64 4 Phaeophyta, unidentified 40.88 28.44 6.66 5.33 0.77 0 0.2 30.6 69.8 35.0 6.2 5.0 0.8 0.2 16.41 5 Ulva spp. 15.00 13.77 12.00 0.10 0 42.8 0 0 0.4 8.6 4.0 6.2 4.8 6.8 8.17 6 Chlorophyta, unidentified 23.55 2.44 12.00 0 1.55 0 0 34.2 26.2 0 9.4 0.2 0 1.2 7.90 7 CoraIlina spp. 24.66 10.66 1.22 0 0 0 2.0 0.2 2.2 16.6 8.4 24.4 2.0 10.0 7.31 8 Collisella scabra 3.00 7.55 9.00 5.88 2.44 1.8 7.6 5.0 5.8 1.2 9.4 7.4 6.4 5.6 5.57 9 Prionitis lanceolata 21.11 0 0 0 0 0 0 0 0 0 0 38.0 0 0 4.22 10 Gigartina leptorhynchos 10.55 5.22 3.11 0.22 0 0 0 0 0 20.0 14.0 0.4 0 0 3.82 11 Mytilusedulis 5.78 10.33 0.10 0 0 29.0 0 0.2 0 0 0 0 0 0 3.24 12 Geramium spp. 11.55 3.11 0 0 �9 0 0 0 0 0 0 0 13.4 13.0 0 2.93 13 Collisella digitalis 0 0.55 4.83 4.55 1.33 6.0 0.2 2.8 0 0 0.4 2.6 2.2 6.2 2.26 14

55 taxa was: 20 primary producers (1 unidentified bacillariophyceae and 19 algae), 16 filter feeders (1 sponge, 4 bryozoans, 2 bivalves, 2 sedentary polychaetes, 5 barnacles, and 2 ascidians), 13 grazers (12 gastropods and 1 echinoid), 1 deposit feeder (1 gammarid amphipod), and 5 predators (3 gastropods and 2 asteroids).

Table 4 ranks the 14 dominant taxa of the 55 taxa recorded in the quantitative survey; their mean abundance among levels and stations is also given. Stress should be placed on the fact, however, that not all taxa presented in Table 4 (also in Tables 1 and 2) are equiva- lent entities. Chthamalus spp., for example, represents groups of C. dalli and C. fissus, small barnacles which could not be separated by species in the field. Similarly, the unidentified Bacillariophycea, Chlorophyta and Phaeophyta are microscopic organisms; they were too small for field identification.

Distribution

Two discrete vertical zones could be recognized throughout the study area (Fig. 7); the upper zone, occupied by barnacles and situated between levels +5 and +3 ft and the lower zone, dominated by Chlorophyta, Phaeophyta, the anemone Anthopleura elegantissima, and the barnacle Tetraclita squamosa rubescens, situated between levels + 3 and 0 ft. The + 3 ft level or mean sea level (MSL) was the boundary between the two zones. These two zones have an estimated percentage of air exposure ranging from 41.3 to 82.8 and 1 to 41.3, respectively (Ricketts and Calvin, 1968).

A dendrogram (Fig. 8) suggests three groupings of stations: Stations l l A , 13A and 23; Stations 65A, 57A and 22A; and Stations 65B, 57B and 22B. These

three groups belong to the shoreline, inner breakwater and outer breakwater, respectively. The breakwater groups were well defined; the shoreline group, however, exhibited a relatively low similarity of species composition between stations.

The barnacles Balanus glandula and Chthamalus spp. were dominant along levels +5, +4 and +3 ft and were characteristic species (P6r~s and Picard, 1964; Loi, 1967) o f the B. glandula-Chthamalus spp. association. Peak abundances of B. glandula and Chthamalus spp. occurred at levels +4 and +3 ft, respectively (Fig. 7). Individuals of these species could, however, be found at higher levels at the outer breakwater stations than at the shoreline stations. In addition, Chthamalus spp. were more abundant than B. glandula at nearly all levels and stations. The latter was abundant only at the shoreline stations, while the former increased in overall abundance from the shoreline stations to the outer breakwater stations.

The Balanus glandula-Chthamalus spp. assemblage often accommodated accompanying species (P6r6s and Picard, 1964; Loi, 1967) of limpets, of which Collisella digitalis and C. scabra were present in low but consistent numbers. The former occurred in smaller numbers and in the upper zone; the latter was more numerous and could be found down to level + 1 ft.

Below level +3 ft, Chlorophyta, Phaeophyta, Corallina sp. Prionitis lanceolata, Anthopleura elegantissima, and Tetraclita squamosa rubescens, were dominant. These organisms tended to be segregated into two related facies, the A. elegantissima-P, lanceolata facies which flourished along the outer breakwater and the A. elegantissima- T. squamosa rubescens facies found along the inner breakwater. At the shoreline stations they were replaced by a mosaic association characterized by the dominance of unidentified green and brown microscopic algae.


r ~.8 ,12 ~-1

0

KEY

O • O Anthopleura elegantissima

Balanus glandula

Ceramium sp.

~i~i: Chlorophyta, unid.

Chthamalus spp.

0 Collisega digitalis

Collisella scabra

_/ Corallina s p p.

[J~ Gigartina leptorhynchos

p Mytilus edulis

Phaeophyta, unid.

Prionitis lanceolata

�9 Tetrac/ita squamosa rubescens

E ~ Ulva s p p.

* \ / Ik it \ ^ .,p" ~

o , ,

-I l" 100 Individuals/contact points , ~ ~ '; ~ " ,' ~ ~ ~f L~J ,~%1

i i i I , i i i i i ~ i i i i i , , i i i i i i

0300 0600 0900 1200 1500 1800 2100 2400 TI M E I h rs l

Fig. 7. Vertical distribution of 14 most abundant taxa throughout study area. MSL: mean sea level (+3 It)

1.0

STATIONS Shore l ine inner Breakwate r Ou te r Breakwate r

11A 13A 23 65A 57A 22A 65B 57B 22B

0 .9

0 ,8

0 7

0 .6

0 . 5

I

w]- L r I

. . . . . . . . ~ = o . 6 2 8 . . . . . . . . . . . J . . . .

I

1 I

Fig. 8. Dendrogram produced by group-averaging technique among 9 intertidal stations; linkage was based on the Czekanowski or SCrensen similarity coefficient

The colonial anemone Anthopleura elegantissima often inhabited exposed surfaces. Its overall density was greatest at the + 1 ft level and downward. The red alga Prionitis lanceolata was also dominant below the + 1 ft level, but only in surf-beaten habitats. The barnacle Tetraclita squamosa rubescens dominated the +2 and + 1 ft levels of the inner breakwater stations. Unidenti- fied green, brown and coralline algae were also wide- spread among the breakwater stations and along levels +2 and + 1 ft. Chlorophyta and Phaeophyta, which are

more tolerant of desiccation than Corallina spp., could be found up to the +4 ft level.

Among the many species present within the lower zone, the algae Ulva sp. and Rhodoglossum affine were particularly common on bare rock; the former was lush at Station l lA on the Navy Mole, the latter at the breakwater stations.

Near the 0 level, Mytilus edulis and Pisaster ochraceus were the most abundant species besides Prionitis lanceolata, Anthopleura elegantissima, and Tetraclita squamosa rubsecens which normally extend further vertically downshore in the intertidal zone. Field observations recorded dense patches of bay mussels at shoreline stations and a large number of seastars on both sides of the breakwater. M. edulis was still found below level 0, but in considerably smaller numbers.

Organisms inhabiting lower levels of the Navy Mole were often coated with silt and oil films; many dead organisms were observed during the survey. Also, they were generally smaller than conspecifics living on the breakwater.

Assemblages at level 0 were qualitatively the richest. Analysis of the scrapings determined 136 taxa compared with 55 taxa recorded in the quantitative survey. Among these, the bryozoan Filicrisia sp., the polychaetes Polyophthalmus pictus, and Typosyllis fasciata, the cheliferan Anatanais normani, the skeleton shrimp Caprella penantis, the gammarid Hyale frequens, and the sea urchin Strongylocentrotus purpuratus were the most common.

Fig. 9 summarizes the vertical and horizontal distribu- tions of the 14 most abundant species throughout the study area. From the shoreline to the outer breakwater there were general increases in both numbers of species and individuals and also in widths of the zones. Addi-


7 ~O Anthopleura olegantissima

* Balanus glandula

Ceramium sp.

6 ~!i: Chl0rophyta, unid.

Chthama/us spp.

0 Col/ise//a d/gl?a//s

Collise//a scabra

v Corallina spp.

~ Gigartina leptorhynchos Mytl/us edufis

Phaeophyta, unid.

Prionitis lanceolata

�9 Tetrac/ita squamosa rubescens

( ~ Ulva s p p.

O

4 , ~ ~ @@ ._= 0

i * ; * , , , : , , , , ,

' 2 ~ ~ ~ ~ a e . ~

,.:......-.."..!: . :..!:.'."~ ~ ~ ~:-,"i?:':.i: ":~

m c ,* !?!.0~176176176

S H O R E L I N E

0.:.::<. ~, #e ~ =~. .-- ~ ~e ~' ~ ' # e ~, o #e #e #e :::('

" ~ ~, #e , ' ~'*' ........ ~a e,~a ~ " (

0 -3

I N N E R B R E A K W A T E R liD-- ~ OUTER B R E A K W A T E R

209

Fig. 9. Diagrammatic distribution of 14 most abundant taxa at various tidal levels and along the shoreline, inner breakwater and outer breakwater

tionally, fewer dead organisms were found at the breakwater stations than at the shoreline stations.

Discussion and Conclusions

The distribution of intertidal flora and fauna on the Pacific coast of North America according to their levels of occurrence has been repeatedly studied (Rasmussen, 1935; Hewatt, 1937; Doty, 1946; Rigg and Miller, 1949; Hedgpeth, 1961, 1962; Stephenson and Stephenson, 1961a,b; Ricketts and Calvin, 1968). Within the Port of Long Beach, the zonation of organisms living on hard substrates between the +5 and 0 ft tidal levels basically agrees with that described by Ricketts and Calvin (1968). The Batanus glandula-Chthamalus spp. assemblage occupies the upper zone and the Mytilus edulis-Pisaster ochraceus assemblage the lower zone, the +3 ft level (mean sea level) being the boundary between the two zones. These two zones correspond to Zones 2 and 3 (Ricketts and Calvin, 1968) or to upper and lower

midlittorals (Stephenson and Stephenson, 1949; P6r6s, 1957;Loi, 1967).

As previously reported, the barnacle zone tended to increase in width from the shoreline stations to the outer breakwater stations because of the increase of wave action from shore to open ocean (Colman, 1933; Lewis, 1964; Loi, 1967; Ricketts and Calvin, 1968). In terms of competition, Balanus glandula and Chthamalus spp. inhabit the same zone and are rivals for both food and primary space. B. glandula, which grows faster and larger, always outcompetes Chthamalus spp., forcing it into a higher zone (see also Connell, 1961). Conse- quently, the barnacle assemblage was found split into two monospecific facies as seen along the outer breakwater.

The distribution of the bay mussel Mytilus edulis was patchy and not continuous as expected (see Ricketts and Calvin, 1968). This was due to the local dominance of Prionitis lanceolata, Anthopleura elegantissima, and Tetraclita squamosa rubescens. These three species established two overlapping facies (A. elegantissima-P.


lanceolata facies along the outer breakwater and A. elegantissima-T, squamosa rubescens facies along the inner breakwater) which partly obscured the under- lying mussel bed. Therefore, M. edulis could be found in large aggregations only in the quieter waters along the shoreline.

The scarcity of Balanus amphitrite, a characteristic species of the warm waters of bays and estuaries having restricted circulation, was unusual. This seems to additionally confirm the open coastal affinities of the studied assemblages.

The intertidal assemblages within Long Beach Port were dominated by suspension feeders in the upper midlittoral and by producers and grazers in the lower midlittoral. Only below mean sea level (+3 ft could one f'md important numbers of predators, of which Pisaster ochraceus was the most conspicuous. This common seastar, preying upon chitons, limpets, bivalves, and barnacles, may have been responsible for the low number of adult bay mussels at the breakwater stations (Feder, 1959, 1970; Mauzey, 1966; Paine, 1966, 1974). P. ochraceus has been reported to be responsible for the maintenance of subclimax assemblage structure typified by absence or restricted occurrence of the climax dominant Mytilus edulis (Paine, 1966; 1974). Exclusion of this important predator results in extensive settlement and growth of mussels and displacement of subclimax species such as Tetraclita squamosa rubescens and large algae. Therefore, predation has a great impact on the structure of midlittoral assemblages within the Port of Long Beach (see also Paine, 1974; Menge, 1976; Menge and Sutherland, 1976; Lubchenco and Menge, 1978).

The relatively low similarity of species composition between stations in the shoreline group (Fig. 8) seems to indicate an instability in the shoreline assemblage because of possible variations in the limiting shoreline environmental factors, including silt and oil. Additionally, the shoreline may be regarded as a transitional area between the more stressed inner harbor and the less stressed breakwater environments (Reish, 1959).

Increases in both species diversity and individual abundance were observed with decreasing tidal level. Since environmental stresses are less severe at lower tidal levels, these trends are expected.

The increase in numbers of species and individuals from the shoreline to the outer breakwater may be related to the improvement in water quality from harbor to ocean (Reish, 1959; Bryant and Associates Inc. et al., 1976). The overall scarcity in species and individuals along the shoreline may be partly attributable to the presence of heavy siltation and oil, as silt and oil Films on the substrate inhibit the settlement of various larvae. Additionally, silt may obstruct the filtering system of several falter-feeders such as bay mussels and barnacles, characteristic inhabitants of the intertidal zone. The exceptionally great abundance of organisms at Station 23 was associated with the presence of a dense algal turf which provides refuges for burrowing forms as well.

Acknowledgements. I wish to acknowledge the indis- pensable assistance of D. Cadien, J. Dorsey, T. Gerlinger, D. Leasure, and S. Sargent for their field work. I extend my special thanks to C. T. Mitchell and Professor J. M. P6rbs who reviewed the manuscript and provided valuable suggestions. This study was partly supported by the Board of Harbor Commissioners of the Port of Long Beach, Long Beach, California.

Literature Cited

Bryant, J. K. and Associates Inc.; Environmental Quality Analysts Inc.; Marine Biological Consultants Inc.; and Converse Davis Dixon Associates Inc.: The Port of Long Beach, Long Beach, California: environmental and geotechnical sampling program. Vol. 1. Final Report, 256 pp. 1976. (Prepared for the Board of Harbor Commissioners, City of Long Beach, Long Beach, California; copies available from: Marine Bio- logical Consultants Inc., 947 Newhall St., Costa Mesa, California 92627, USA)

Colman, J.: The nature of the intertidal zonation of plants and animals. J. mar. biol. Ass. U.K. 18, 435-476 (1933)

Connell, J. H.: The influence of interspecific competition and other factors on the distribution of the barnacle, Chthamalus stellatus. Ecology 46, 831-844 (1961)

Czekanowski, J.: Zur differential Diagnose der Neandertalgruppe. KorrespB1. dt. Ges. Anthrop. 40, 44-47 (1909)

Day, J. H.,J. G. Field and M. Montgomery: The use of numerical methods to determine the distribution of the benthic fauna across the continental shelf of North Caxolina. J. Anim. Ecol. 40, 93-125 (1971)

Doty, M. S.: Critical tide factors that are correlated with the vertical distribution of marine algae and other organisms along the Pacific coast. Ecology 27, 315-328 (1946)

Environmental Quality Analysts Inc. and Marine Biological Consultants Inc.: Long Beach Generating Station marine monitoring studies. Vols 1 and 2. 1974 Annual Report, 228 pp. 1975. (Prepared for Southern California Edison Company, Los Angeles, California; copies available from: Marine Biological Consultants Inc., 947 Newhall St., Costa Mesa, California 92627, USA)

Feder, H. M.: The food of the starfish, Pisaster ochraceus, along the California coast. Ecology 40, 721-724 (1959)

Feder, H. M.: Growth and predation of the ochre seastar, Pisaster ochraceus (Brandt) in Monterey Bay, California. Ophelia 8, 161-185 (1970)

Field, J. G.: A numerical analysis of changes in soft-bottom fauna along a transect across False Bay, South Africa. J. exp. mar. Biol. Ecol. 7, 215-253 (1971)

GoodaU, D. W.: Some considerations in the use of point quadrats for the analysis of vegetation. Aust. J. scient. Res. (Set. B) 5, 1-41 (1952)

Grieg-Smith, P.: Quantitative plant ecology, 256 pp. London, England: Butterworths 1964

Hedgpeth, J. W.: Common seashore life of Southern California, 64 pp. Healdsburg: Vinson Brown 1961

Hedgpeth, J. W.: Introduction to seashore life of the San Francisco Bay region and the coast of northern California, 136 pp. Berkeley, California: University of California Press 1962

Hewatt, W. G.: Ecological studies on related marine intertidal communities of Monterey Bay, California. Am. Midl. Nat. 18, 161-206 (1937)

Lewis, J. R.: The ecology of rocky shores, 323 pp. London: English University Press 1964

Loi, T-n.: Peuplements animaux et v6g6taux du substrat dur intertidal de la bale de Nha Trang. M6m. Inst. oc6anogr. Nhatrang 11, 1-236 (1967)

Tran-ngoe Loi: Environmental Stresses and Intertidal Assemblages

Lubchenco, J. and B. A. Menge: Community development and persistence in a low rocky intertidal zone. Ecol. Monogr. 48, 67-94 (1978)

Mauzey, K. P.: Feeding behavior and reproductive cycles in Pisaster ochraceus. Biol. Bull. mar. biol. Lab., Woods Hole 131,127-144 (1966)

Menge, B. A.: Organization of the New England rocky intertidal community: role of predation, competition, and environmental heterogeneity. Ecol. Monogr. 46, 355-393 (1976)

Menge, B. A. and J. P. Sutherland: Species diversity gradients: synthesis of the roles of predation, competition and temporal heterogeneity. Am. Nat. 110, 351-369 (1976)

Paine, R. T.: Food web complexity and species diversity. Am. Nat. 100, 65-75 (1966)

Paine, R. T.: Intertidal community structure: experimental studies on the relationship between a dominant competitor and its principal predator. Oecologia 15, 93-120 (.1974)

P6r~s, J. M.: Le probl~me de l'6tagement des formations benthiques. Reel Trav. Stn max. Endoume 12, 4-21 (1957)

P6r~s, J. M. et J. Picard: Nouveau manuel de bionomie benthique de la met M6diterran6e. Reel. Tray. Stn mar. Endoume 3I, 1 - 4 7 (1964)

Pielou, E. C.: Shannon's formula as a measure of specific diversity: its use and misuse. Am. Nat. 100, 463-465 (1966)

Rasmussen, D. I.: Southern California Balanus-Littorina communities: effects of wave action and friable material. Ecol. Monogr. 5, 304-308 (1935)

Reish, D. J.: An ecological study of pollution in Los Angeles- Long Beach Harbors, California. Oce. Pap. Allan Hancock Fdn 22, 1-119 (1959)

Rieketts, E. F. and J. Calvin: Between Pacific tides, 614 pp.

211

4th ed. Revised by J. W. Hedgpeth. Stanford, California: Stanford University Press 1968

Rigg, G. B. and R. C. Miller: Intertidal plant and animal zonation in the vicinity of Neah Bay, Washington. Proc. Calif. Acad. Sei. 26, 323-351 (1949)

Shannon, C. E. and W. Weaver: The mathematical theory of communication, 111 pp. Urbana, Illinois: University of Illinois Press 1963

SCrensen, T.: A method for establishing groups of equal ampli- tude in plant sociology based on similarity of species content and its application to analyses of the vegetation on Danish commons. K. danske Vidensk. Selsk. Skr. 5, 1-34 (1948)

Southwood, T. R. E.: Ecological methods, with particular reference to the study of insect populations, 391 pp. London: Methuen Co. Ltd. 1966

Stephenson, T. A. and A. Stephenson: The universal features of zonation between tide-marks on rocky coasts. J. Ecol. 37, 289-305 (1949)

Stephenson, T. A. and A. Stephenson: Life between tide-marks in North America. IVA. Vancouver Island I. J. Ecol. 49, 1-29 (1961a)

Stephenson, T. A. and A. Stephenson: Life between tide-marks in North America. IVB. Vancouver Island II. J. Ecol. 49, 227-243 (1961b)

Tide Tables: U.S. Department of Commerce; National Oceanic and Atmospheric Administration 1975. (Copies available from: National Ocean Survey, Roekvllle, Maryland 20852, USA)

Date of final manuscript acceptance: March 6, 1981. Communicated by J. M. P6r6s, Marseille

environmental stresses and intertidal assemblages on hard substrates in the port of long beach,...

Documents