Fatty acid composition and lipid content in the copepod Limnocalanus macrurus during summer in the southern Bothnian Sea

Abstract

The lipid reserves and occurrence of the cold-stenothermic, omnivorous copepod Limnocalanus macrurus were studied in the Bothnian Sea (northern Baltic Sea) during spring and summer 2013-2014 with a special emphasis on the fatty acid composition of adults and their potential food. The individual total wax ester (WE) content, determined from the size of oil sacs in the prosoma, ranged on average from 1.3 to 2.6 µg, and showed a decreasing trend towards September. Lipids were dominated by fatty acids 16:0, 18:1(n-9), 18:2(n-6), 20:5(n-3) and 22:6(n-6), forming 56-61% of total fatty acids in June-September. Decreasing abundance of adults and reduction of the lipid storage implied that during summer adults suffered from starvation and, as a result, became eliminated from the population. The lipid content and dietary fatty acid markers suggested that in May, adult L. macrurus utilized the phytoplankton bloom, consisting mainly of diatoms and dinoflagellates, but later, during July-September, consumed either algae or heterotrophic organisms sinking from upper water layers or crustaceans inhabiting the same deeper water layers as L. macrurus. In the face of the climate change, the rising temperatures may force L. macrurus permanently to deeper water levels. If also the food resources are limited, we conclude that the summer season may act as a bottleneck limiting the propagation of L. macrurus and having implications further along the food web.

Plankton biodiversity and species co-occurrence based on environmental DNA – a multiple marker study

“…The significant positive correlations may also reflect the zooplankton presence following the presence of its prey, e.g. copepod Limnocalanus macrurus and diatoms Melosira arctica and Skeletonema marinoi (Mäkinen et al 2017) or ciliates and Heterocapsa triquetra (Stoecker and Evans 1985;Hansen, 1995). However, zooplankton generally avoids grazing on toxin-producing phytoplankton species, e.g.…”

Fatty acid profiles reveal dietary variability of a large calanoid copepod Limnocalanus macrurus in the northern Baltic Sea

“…L. macrurus is a cold-stenothermic copepod that dwells in deep water layers and is widely distributed in lake ecosystems, but also in the Baltic Sea, where it is considered as a glacial relict (Kane et al, 2004;Hiltunen et al, 2014;Einberg et al, 2019). It is an opportunistic omnivorous feeder: it preys on other copepods (Warren, 1985;Dahlgren et al, 2012) and utilizes phytoplankton blooms (Hirche et al, 2003;Mäkinen et al, 2017a). Weak tolerance to high temperatures makes L. macrurus vulnerable to climate change; high water temperatures in the upper water column may restrict its access to food (Mäkinen et al, 2017a), while hypoxia and eutrophication may further reduce its abundance (Kane et al, 2004).…”

“…It is an opportunistic omnivorous feeder: it preys on other copepods (Warren, 1985;Dahlgren et al, 2012) and utilizes phytoplankton blooms (Hirche et al, 2003;Mäkinen et al, 2017a). Weak tolerance to high temperatures makes L. macrurus vulnerable to climate change; high water temperatures in the upper water column may restrict its access to food (Mäkinen et al, 2017a), while hypoxia and eutrophication may further reduce its abundance (Kane et al, 2004). Although the lowoxygen layers in the water column may serve as refuges against predation (Webster et al, 2015), L. macrurus benefits physiologically from high oxygen and low temperature via increased antioxidant activity (Vuori et al, 2015).…”

“…Although the lowoxygen layers in the water column may serve as refuges against predation (Webster et al, 2015), L. macrurus benefits physiologically from high oxygen and low temperature via increased antioxidant activity (Vuori et al, 2015). Previous studies have described the seasonality of the fatty acid profiles of L. macrurus in lakes (Hiltunen et al, 2014) and in the Gulf of Bothnia (Dahlgren et al, 2012;Mäkinen et al, 2017a), but largescale spatial comparisons in the Baltic Sea are not conducted.…”

Photo- and autoxidation of unsaturated algal lipids in the marine environment: An overview of processes, their potential tracers, and limitations

“…The majority of studies into the degradation of phytoplanktonic organic matter to date have focused on biotic degradation processes (bacterial degradation, zooplanktonic grazing, macrofaunal degradation) (e.g., Afi et al, 1996;Sun et al, 1999;Mäkinen et al, 2017). In contrast, the role played by photochemical and free radical-mediated processes in the degradation of lipid components during the senescence of phototrophic organisms has only recently been investigated (Rontani et al, 2007a(Rontani et al, , 2011(Rontani et al, , 2014aChristodoulou et al, 2010;Amiraux et al, 2016).…”