Taxonomic, Temporal, and Spatial Variations in Zooplankton Fatty Acid Composition in Puget Sound, WA, USA

Fatty acid (FA) content and composition of zooplankton in Puget Sound, Washington (USA) was studied to investigate the nutritional quality of diverse zooplankton prey for juvenile salmon (Oncorhynchus spp.) in terms of their essential fatty acid (EFA) content. The study focus was on eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and arachidonic acid (ARA) as these are key FA needed to maintain growth and development of juvenile fish. The different zooplankton taxa varied in their FA composition. Much of the variation in FA composition was driven by 18:1ω9 (a biomarker of carnivory), ARA, DHA, and FA characteristic of diatoms, which are linked to zooplankton diet sources. Gammarid and hyperiid amphipods contained the highest amount of EFA, particularly the gammarid amphipod Cyphocaris challengeri, while shrimp and copepods had much lower EFA content. Crab larvae, which are important prey for juvenile salmon in Puget Sound, had intermediate EPA + DHA content and the lowest DHA/EPA ratio, and were rich in diatom biomarkers. Temporal and spatial trends in zooplankton lipids were less apparent than the taxonomic differences, although the EFA content increased from spring to summer in Cancridae zoeae and the amphipod C. challengeri. These results on taxon-specific EFA content provide baseline information on the nutritional quality of zooplankton that can be applied in food web models. Combining zooplankton fatty acid data (quality) with taxon-specific zooplankton biomass data (quantity) enables development of new, sensitive indicators of juvenile fish production to help assess recent declines in salmon production in the Pacific Northwest and predict future adult returns.

Selective Fatty Acid Retention and Turnover in the Freshwater Amphipod Pallaseopsis quadrispinosa

Gammarid amphipods are a crucial link connecting primary producers with secondary consumers, but little is known about their nutritional ecology. Here we asked how starvation and subsequent feeding on different nutritional quality algae influences fatty acid retention, compound-specific isotopic carbon fractionation, and biosynthesis of ω-3 and ω-6 polyunsaturated fatty acids (PUFA) in the relict gammarid amphipod Pallaseopsis quadrispinosa. The fatty acid profiles of P. quadrispinosa closely matched with those of the dietary green algae after only seven days of refeeding, whereas fatty acid patterns of P. quadrispinosa were less consistent with those of the diatom diet. This was mainly due to P. quadrispinosa suffering energy limitation in the diatom treatment which initiated the metabolization of 16:1ω7 and partly 18:1ω9 for energy, but retained high levels of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) similar to those found in wild-caught organisms. Moreover, α-linolenic acid (ALA) from green algae was mainly stored and not allocated to membranes at high levels nor biosynthesized to EPA. The arachidonic acid (ARA) content in membrane was much lower than EPA and P. quadrispinosa was able to biosynthesize long-chain ω-6 PUFA from linoleic acid (LA). Our experiment revealed that diet quality has a great impact on fatty acid biosynthesis, retention and turnover in this consumer.

Comparative Morphology of Dendrocometes Paradoxus (Ciliophora, Suctorea) from Two Distant Regions (Ukraine And Mexico) and Different Host Species

Comparative analysis of Dendrocometes paradoxus Stein, 1852 cell morphology from various gammarid amphipod species in different regions of Ukraine, and those attached to several host body parts of Hyalella azteca collected in two Mexican lakes, was carried out in order to demonstrate the morphological variability, due to the hosts species or their geographical distribution. For hosts species and corporal distribution, no significant differences between the two populations were shown. As the result, it was found the suctorians common for amphipod crustaceans from Ukraine and Mexico all are conspecific and belong to D. paradoxus.

Effects of nutrient additions on intertidal seagrass (Zostera muelleri) habitat in Western Port, Victoria, Australia

Loss of seagrass habitat in many parts of the world has been attributed to increases in nutrient loading to nearshore areas. The role of excess epiphyte, macroalgal or phytoplankton growth in shading of seagrass leaves and negatively affecting seagrass health is generally agreed to be a prevalent mechanism in seagrass decline worldwide. In the present study nutrient addition experiments were undertaken at three sites in Western Port, Victoria. Nutrients were added to the water column using the controlled release fertiliser Osmocote™ in late summer 2005. The experiments ran for one month at two of the sites (Blind Bight and Hastings) and at the third site (Crib Point) the experiment ran for three months. Control and nutrient addition plots were monitored for concentrations of inorganic nutrients, number of seagrass leaves, seagrass, epiphyte and loose algal biomass and invertebrate faunal assemblages. Nutrient additions had increased ash free dry weight of seagrass leaves and loose algae at two of the three sites studied. There was also an increase in gammarid amphipod densities at the Crib Point site. We consider that Western Port seagrass habitat is sensitive to increased loads of nutrients within the water column with the Blind Bight region most at risk.