Phytoplankton Size Distribution Research Articles

Size Distribution of phytoplankton in the central and eastern tropical Pacific

Size separations of phytoplankton biomass and production were performed with Nuclepore filters in the central and eastern tropical Pacific. The results show that there is a relationship between size and distance from land forms, with larger aggregates of phytoplankton dominating close to shore and small (less than 1 μm) forms dominating offshore. Surface nutrient concentrations were high in the offshore regions of equatorial upwelling and there was no apparent relationship between nutrient concentration and size. The phytoplankton biomass and production in the equatorial Pacific from 90°W to 150°W are dominated by small algae which are not retained by 5 μm Nuclepore filters with these organisms accounting for over 80% of the biomass and production. It is hypothesized that the dominance of small forms, as well as the relatively low plant biomass found, is the result of the absence of neritic bloom‐forming centric diatoms in offshore regions. The fact that small phytoplankton dominate in the equatorial Pacific suggests a dynamic food web. A dynamic food web coupled with the vigorous horizontal circulation of the equatorial Pacific supports the notion that some of the new nitrogen upwelled in this region is first exported laterally and then vertically.

Plankton community structure and size spectra in the Georgian Bay and North Channel ecosystems

Patterns in the size distribution and taxonomic composition of phytoplankton and zooplankton communities for 1974 in Georgian Bay and the North Channel are described. The Diatomeae predominate the phytoplankton in both areas. Copepods, particularly Calanoida, comprise the greatest fraction of the zooplankton biomass. Normalized plankton biomass spectra for both ecosystems are typical of those found in Lake Superior and offshore Lake Huron. The plankton communities of Georgian Bay and the North Channel are thus similar to the most oligotrophic of the Laurentian Great Lakes.

Contrasting Patterns of Net- and Nanoplankton Production and Biomass among Lakes

The relative contribution of nanoplankton to total algal biomass was shown to be negatively correlated with total phosphorus during summer over a wide range of lakes. We hypothesize that this pattern can be explained either by changes in the relative growth rates of net- or nanoplankton with increased nutrient levels, or through the regulation of the nanoplankton biomass by herbivores, allowing disproportionate increases in netplankton biomass in more eutrophic systems. These explanations were tested by examining the relationships between net primary production (grams of carbon per cubic metre per year) and biomass (micrograms per litre) of these size fractions and total phosphorus concentrations (micrograms per litre) using literature data from lakes through-out the world. The production of the net- and nanoplankton vary similarly with total phosphorus, while the biomasses (and thus the ratios of production to biomass) of the two groups show significantly different relationships. Our results support the hypothesis that changes in the size distribution of summer phytoplankton with enrichment seem to be influenced more by herbivores than by changes in the relative growth rates of the two size fractions.

Vertical size distribution of phytoplankton in the western Mediterranean Sea during early summer

Vertical size distribution of phytoplankton in the western Mediterranean Sea during early summer

Formulation of an ingestion function for a population of Paracalanus feeding on mixtures of phytoplankton

The effective food concentration concept is extended to modelling the ingestion of a Paracalanus population based on feeding experiments by Paffenhöfer, who simulated phytoplankton size distributions and concentrations of Gulf Stream intrusions in the South Atlantic Bight shelf. The effective food concentration concept uses selectivity coefficients, calculated for each phytoplankton size class and copepod developmental stage, to weight food concentration in Ivlev relations between ingestion and food concentration. These selectivity coefficients for each phytoplankton size class are formulated as functions of copepod weight and phytoplankton concentration. Parameters of the Ivlev curves are also made functions of copepod weight. The resulting ingestion equation is discussed within the context of copepod feeding, and applied to phytoplankton size distributions and concentrations typical of Gulf Stream intrusions.

The transport of oyster larvae in an estuary

Vertical and horizontal distributions of 3 larval stages of the oyster Crassostrea virginica were measured concurrently with phytoplankton species compositions, phytoplankton size distributions and physical hydrographic parameters in tributaries of the Chesapeake Bay (USA) during the oyster spawning seasons of 1980 and 1981. The superposition of the biological distributions upon the physical hydrographic data provide instantaneous distributions of the entire system which are consistent with the upstream transport of oyster larvae. Oyster larvae distributions in the Choptank River and its Broad Creek and Tred Avon River tributaries can be described in terms of three contiguous regions: (1) a common spawning region, (2) an intermediate, upstream transport region and (3) a seed bed region where major spat set occurs. The phytoplankton species compositions and abundances in the size fraction less than 10 μm in the tributary system during the transport were sufficient to supply optimum growth requirements of developing larvae. The transport proposed can explain the 30 yr record of consistently higher spat set success in one tributary, Broad Creek, relative to an adjoining tributary, the Tred Avon River. This may be a general mechanism whereby oysters maintain reproductive success and emigrate to seed bed regions in the Chesapeake Bay.

The size distribution of phytoplankton and participate organic matter in the Equatorial Atlantic Ocean: importance of ultraseston and consequences

The size fractionation of particulate matter (<200, <35, <3 and <1 am) has been measured in the Equatorial Atlantic Ocean at different stations. Chlorophyll u, phaeophytin, par- ticulate carbon, nitrogen and phosphorus have been analysed. Primary production by 14C02 uptake was also measured with prescreening technique. It appears from this study, that the particulate matter has a very small size: 40-60% of the chlorophyll passed through 1 pm Nucleopore filter, and 75-90% of the particulate carbon and nitrogen passed through 3 pm Nucleopore filter in offshore waters. From the atomic ratio C/N, C/P and C/chla, and primary production values, the < 3 Fm fraction would be mainly constituted by inactive photosynthetic organisms or particles of detritus. The 3-35 pm fraction, in contrast, would be principally active phytoplankton.