Simenstad, C.A., R.M. Thom, K.A. Kuzis, J.R. Cordell and D.K. Shreffler. 1988. Nearshore community studies of Neah Bay, Washington. Report to U.S. Army Corps of Engineers. University of Washington. Wetland Ecosystem Team. Fisheries Research Institute. FRI-UW- 8811. 114pp.

Region: PNW Species: Macrophyte, fish, benthic macroinvertebrate epibenthos, pelagic zooplankton assemblages.

Study Objectives: Impact assessment in response to proposed projects to develop intertidal and subtidal areas for log shipping and commercial fishing boat moorage. In the context of the proposed projects, evaluate the functions and relative importance of nearshore macrophyte habitats: 1) compare fish and invertebrate assemblage structure and standing stock between macrophyte and non-macrophyte habitats, 2) evaluate the function of these macrophyte habitats, 3) document seasonal variation in structure, production and function of macrophyte habitats,
4) evaluate functional contributions of macrophyte communities to adjacent, non-macrophyte habitats, and 5) hypothesize and estimate consequences to nearshore communities of macrophyte habitat loss and/or degradation in habitat quality. Study is organized around five basic components: 1) fish and motile macroinvertebrate assemblages, 2) epibenthos and pelagic zooplankton assemblages, 3) benthic infaunal macroinvertebrates, 4) macrophyte assemblages, and 5) ecological interactions.

Study Methods: Beach seine, purse seine, Otter Trawl, benthic grab sampling, epibenthos pump sampling, infaunal bivalve suction pump sampling, underwater transect surveys, quadrats, oxygen flux measurements for net seaweed primary productivity estimates for four sites: Baadah Point, Evans Mole, Crown Z, and Turning Basin.

Fish and Motile Macroinvertebrates Results: Baadah Point showed 40 fish species, twice the number of species observed at other sites, with increased diversity in numerical composition and no one species predominating. While, at Evans Mole Pacific staghorn sculpins dominated at 44%, and at Crown Z. shiner perch dominated for 73% of the standing crop of fishes. Four species of juvenile Pacific salmon occurred: chum, coho, chinook and pink. Chums were collected at all sites in May and July 1986 and March 1987. Coho and pink were captured in July and were abundant at the Baadah Point end of the Bay. Chinook occurred at all sites in September.

Epibenthos Results: harpacticoid copepods were the predominant organisms at all sites except near the Crown Z. dock, comprising 55% of the numerical composition at Baadah Point at 0.0. m and 83% at Baadah Point subtidal Z. marina. In contrast the Crown Z. dock was not dominated by any single taxa. Rather, dominance was shared by unidentified invertebrate eggs.

Pelagic Zooplankton Results: 1) harpacticoid copepods were prominent at Baadah Pint and at the head of the bay, but not at Crown Z. dock and Evans Mole, 2) calanoid copepods were abundant at head of the bay and Evans Mole, 3) barnacle were numerous at Crown Z dock and Evans Mole, and 4) crab zoeae occurred in moderate numbers at all sites except the head of the bay.
Benthic Taxa Results: Gammarid amphipods, polychaete annelids, and bivalves were prominent. Polychaetes and bivalves were the most prominent taxa in biomass. Eleven taxa of infaunal bivalves were identified. Macroinvertebrate infauna densities were similar across sites.

Habitat Utilization Results: herring, smelt, sand lance and salmonids appeared extensively as juveniles but showed no site specificity. Dungeness crabs appeared to move around within the Bay with highest densities at Evans Mole and Crown Z in July and September. Juvenile, sub adult, and adult shrimp at various depths and sites across the bay. Densities of shrimp species were highest near the mouth of the bay.



Factors Affecting Epibenthos and Pelagic Zooplankton Structure and Standing Stock: Epbenthic/epiphytic harpacticoid copepods predominated at Baadah Point and Head of Bay. While more planktonic, barnacles, calanoid copepods and crab zoeae predominated at Evans Mole and Crown Z. sites. Epibenthic harpacticoids were particularly high in September in Z. marina beds at head of the bay while low abundances were found on the Z. marina at Baadah Point which receives higher wave energy.

Trophic Relationships Between Fish and Zooplankton: Macrophytic habitats, such as Z. marina, represent direct and indirect sources of fish prey resources due to the unique associations between seagrasses, seaweeds, kelp and prey organisms (i.e. harpacticoid copepods and amphipods). Harpacticoids occur in the diets of many juvenile fish and are characteristic of seagrass and other habitats with epiphytic diatoms and microalgal growth. Indirectly, eelgrass and other macrophytes support epibenthos and other detritivores by the production of detritus.

Macrophyte Assemblages and Net Primary Productivity: Baadah Point represents a rocky outcrop with a species-rich, abundant and productive seaweed-dominated habitat. Crown Z. and at the Head of the Bay had few species and generally less abundant algal flora with the exception of the dense stand of eelgrass immediately south of the Head of the Bay. Substrata differences, exposure to currents, and present and historical levels of disturbance may explain differences among sites. Baadah Point at head of bay receives nutrient rich inputs. Due to the geomorphic structure of Baadah Point benthic scouring does not tend to occur and the community is relatively undisturbed by sediment movement. This could explain the stable seaweed community developing at this site. Due to cliffs and small freshwater stream at Head of the Bay, sediments are fine and cover much of the bottom with no rocky outcrops. Therefore, shifting sediments play a greater role in regulating assemblage structure. Crown Z. site biologically impoverished state is anomalous due to increased turbidity, lower tidal exchange, log bashing, log storage and debris.

Conclusions: Deepening the channel would not likely change the Bay's primary production potential as increased residence time would likely increase phytoplankton and zooplankton production. However, secondary benthic production would probably shift qualitatively to less diverse, polychaete-dominated assemblages characteristics of deeper, finer sediment habitats and potentially decrease production of specific taxa between the turning basin and other habitats.
Decreased current velocities at the entrance and eastern region of the Bay would increase deposition of fine sediment and detritus east of the turning basin and extend the deposit-feeding assemblages.

However, loss and disruption of habitat by dredging and filling for the marina could significantly decrease diversity and production of macrophyte, demersal fish, motile macroinvertebrate, epibenthos and benthos diversity, and production with the magnitude dependent upon the site chosen.

Short-term Effects of Dredging and Filling: Release toxicants from benthic sediments, increase turbidity during dredging and modify natural environmental characteristics such as sound and light which impact behaviors in pelagic fish. Fish would avoid an of abnormally high sound and turbidity. Therefore, if the dredging operations were to occur between March and October, the result could be the exclusion of pelagic fishes from planktonic food resources. Dredging at the mouth of the bay could effectively close off the bay to any immigration during the periods of operation.