|Seasonal composition of meroplankton and holoplankton in the Bristol Channel|
Williams, R.; Collins, N.R. (1986). Seasonal composition of meroplankton and holoplankton in the Bristol Channel. Mar. Biol. (Berl.) 92(1): 93-101
In: Marine Biology. Springer: Heidelberg; Berlin. ISSN 0025-3162, more
Seasonal distribution; ANE, British Isles, Bristol Channel [Marine Regions]; Marine
|Authors|| || Top |
- Williams, R.
- Collins, N.R.
A decreasing gradation in the plankton standing stock of the Bristol Channel was observed from the seaward section to the inner, less saline, reaches. Two sub-regions of our survey, the North Outer Channel (NOC) and the Inner Channel (IC), represented the extremes of this gradient and were selected for detailed comparison. The integrated zooplankton biomass, over the 307 d sampling period (4 November 1973 to 6 September 1974), was 2 475 mg C m-3 (~266 mg C m-2 d-1) in the NOC and 335 mg C m-3 (~20 mg C m-2 d-1) in the IC. The omnivorous plankton accounted for 76% of the standing stock in the NOC and 89% in the IC, of which 58 and 23% were meroplankton and 39 and 71% were holoplankton, respectively; the remainder was unassigned. The majority of the meroplankton in both subregions was decapod larvae and adults, whereas the holoplankton biomass was dominated in the NOC by copepods (89%) and in the IC by mysids (57%), mainly Schistomyzis spiritus. Centropages hamatus was the most abundant copepod species in the NOC and accounted for 32% of the total holoplankton omnivore standing stock. In the NOC and IC, the carnivorous plankton accounted for 24 and 11% of the total plankton biomass, respectively. In the two sub-regions, 20 and 21% of the carnivores were meroplanktonic (primarily larvae of sprats and pilchards), while the holoplankton carnivores contributed 75 and 74% to the NOC and IC, respectively (Sagitta elegans, Pleurobrachia pileus). S. elegans dominated the holoplankton carnivore biomass for the majority of the year and accounted for 96% in the NOC and 60% in the IC. The integrated total particulate carbon over the 307 d period was 200 g C m-3 (~6 600 g C m-2) in the NOC and 838 g C m-3 (~15 084 g C m-2) in the IC. The annual primary production ranged from 164.9 g C m-2 yr-1 in the Outer Channel (North and South) to 6.8 g C m-2 yr-1 in the IC. The zooplankton biomass reached a maximum in July. The total particulate carbon (TPC) in July was 400 mg C m-3 in the NOC of which ca. 78 mg C m-3 were phytoplankton and ca. 21 mg C m-3 were zooplankton; these values compare favourably with those found in the adjoining Celtic Sea. In the IC, the TPC was 2 800 mg C m-3, of which ca. 107 mg C m-3 were "phytoplankton" and 2.8 mg C m-3 were zooplankton. From the low primary production estimates for the IC it can be concluded that the majority of the chlorophyll, like the TPC, was allochthonous in origin. Furthermore it is suggested that zooplankton plays a minor role in this estuarine ecosystem and is not the main consumer of the suspended particulate carbon; the benthic filter-feeding communities are presumed to fulfill this role in the Bristol Channel.