We studied the naupliar development of the calanoid copepod Calanus glacialis, a key herbivore in the Arctic marine ecosystem. Eggs obtained from females collected at 78° N in Svalbard, Norway, in May 2008 were reared at -1.2°C in a temperature-controlled room. Stage-specific naupliar development time, survival and naupliar size were studied in response to different food qualities, i.e. low versus high proportions of polyunsaturated fatty acids (PUFAs) and low versus high element molar ratios (C:N and C:P). Length measurements of consecutive naupliar stages were obtained from image analysis of digital photos taken every second day. A length-frequency analysis revealed distinct size classes for each stage. Stage duration of the 6 naupliar stages varied between 6 and 27 d. The longest stage duration was measured for Stage NIII. Development time from hatching to Stage NVI was shortest (41.9 d) for nauplii reared under high algal bloom chlorophyll a (chl a) concentrations (~20 µg chl a l -1 ) with algae of high food quality (control). Starved nauplii developed the slowest and showed highest mortality. High mortality was also recorded for nauplii fed with algae grown under a phosphorous limitation that were offered at the same chl a concentrations as the control treatment. These algae had lower PUFA concentrations and higher element molar ratios and were, thus, of lower food quality than the control algae. However, comparable development times and naupliar sizes were found for nauplii fed with algae of high or low food quality. This is the first study that successfully follows the entire naupliar development of Calanus glacialis at subzero temperatures.KEY WORDS: Naupliar development · Temperature · Food quality · Naupliar size 429: 111-124, 2011 ered an adaptation to the short and unpredictable productive season at high latitudes in ice-covered waters (Conover & Huntley 1991, Falk-Petersen et al. 2009. Resale or republication not permitted without written consent of the publisherMar Ecol Prog SerCalanus glacialis reproduction and naupliar growth normally take place in ice-covered seas at water temperatures close to the freezing point of seawater (-1.8°C at salinity 34.8). Data on C. glacialis naupliar development times are, however, scarce and to our knowledge only Corkett et al. (1986) and McLaren et al. (1988) have estimated the development time of C. glacialis nauplii. Naupliar development times have been studied in other Calanus species, such as the North Atlantic species C. finmarchicus (Hygum et al. 2000, Campbell et al. 2001, Cook et al. 2007), C. hyperboreus (Corkett et al. 1986) and C. helgolandicus (Cook et al. 2007, Bonnet et al. 2009), as well as C. pacificus (Mullin & Brooks 1970a, Landry 1983, C. sinicus (Uye 1988), C. australis (Peterson & Painting 1990) and C. marshallae (Peterson 1986). However, these rearing experiments have been conducted at temperatures well above 0°C (2 to 20°C), and measurements of development time of any Calanus species in water temperatures close to the freezing ...

Cryophilic algae thrive in liquid water within snow and ice in alpine and polar regions worldwide. Blooms of these algae lower albedo (reflection of sunlight), thereby altering melting patterns (Kohshima, Seko & Yoshimura, 1993; Lutz et al., 2014; Thomas & Duval, 1995). Here metagenomic DNA analysis and satellite imaging were used to investigate red snow in Franz Josef Land in the Russian Arctic. Franz Josef Land red snow metagenomes confirmed that the communities are composed of the autotroph Chlamydomonas nivalis that is supporting a complex viral and heterotrophic bacterial community. Comparisons with white snow communities from other sites suggest that white snow and ice are initially colonized by fungal-dominated communities and then succeeded by the more complex C. nivalis-heterotroph red snow. Satellite image analysis showed that red snow covers up to 80% of the surface of snow and ice fields in Franz Josef Land and globally. Together these results show that C. nivalis supports a local food web that is on the rise as temperatures warm, with potential widespread impacts on alpine and polar environments worldwide.

Light-dependent behavior of the abundant zooplankton species inhabiting the White Sea were studied experimentally during: (i) the spring equinox (March); (ii) the polar day (late May to June), (iii) August, 17/7 h day-night light cycle, (iv) the fall equinox (October). Behavioral patterns were investigated for eight species of Copepoda (Metridia longa, Calanus glacialis, Pseudocalanus minutus, Oithona similis, Oncaea borealis, Temora longicornis, Centropages hamatus, Acartia spp.), one Cladocera species (Evadne nordmanni) and Polychaeta larvae. The hypothesis was tested that attraction to (or repulsion from) light is the primary mechanism involved in the vertical migration of zooplankton with different trophic characteristics in relation to phytoplankton-rich upper water layer. The impact of red (680 nm), yellow (560 nm) and UV (280 nm) light was tested. The animals were acclimated to two food conditions: natural seawater (satiated) and filtered (1 mm) seawater (hungry). The positive light response of predominantly herbivorous and omnivorous copepods and cladocerans inhabiting the photic water layer corresponds with their distribution and their food vertical distribution. Hungry animals display the strongest responses to light. Light effects on behavior were weak in deep-dwelling O. borealis. We suggest that red and yellow light is an indicator of the photic layer (high food concentration) to zooplankton groups that feed on phytoplankton. In contrast, diapausing (e.g. non-feeding) copepods totally avoid light, especially when they hibernate in the aphotic layer. We hypothesize that there is a relationship between the light response of the zooplankton, their trophic characteristics, migration behavior (diel and ontogenetic) and the water layer occupied.

No abstract

Cryophilic algae thrive in liquid water within snow and ice in alpine and polar regions worldwide. Blooms of these algae lowers albedo (reflection of sunlight), thereby altering melting patterns (Kohshima et al. 1993;Lutz et al. 2014;Thomas & Duval 1995) . Here metagenomic DNA analysis and satellite imaging were used to investigate red snow in

Seasonal dynamics of major biochemical features were studied for three abundant egg-diapausing copepods Acartia biWlosa, Centropages hamatus and Temora longicornis, in the White Sea (66°N), between June 2002 and September 2002. Dry weight (DW) and prosome length varied from 0.54 g ind ¡1 and 0.163 § 0.012 mm (A. biWlosa, CI) to 9.58 § 0.72 g ind ¡1 and 1.135 § 0.167 mm (C. hamatus, females). C org and N org content reached up to 5.91 § 0.44 and 1.23 § 0.09 g ind ¡1 (C. hamatus, females). Protein and lipid content varied greatly from 31.8 to 67.3% DW and from 8.7 to 42.6% DW, respectively. These species show somewhat diVerent biology compared to species at lower latitudes. The copepods use lipid stores to survive during short-term food shortage (e.g. in autumn) and successfully complete their life cycle. In the isolated White Sea during last post-glacial period, species probably evolved some special biochemical features (especially wax esters presence). Food quality demands and long ice coverage are possible factors limiting early development of species in spring.

We have studied the seasonal dynamics of abundance and feeding characteristics of three species of calanoid copepods (Acartia spp., Centropages hamatus and Temora longicornis) in the White Sea from the surface water layer (0-10 m), in order to assess their role in the pelagic food web and to determine the major factors governing their population dynamics during the productive season. These species dominated in the upper water layer (0-10 m) from June through September, producing up to 3 generations per year. Data on the food spectra revealed all species to be omnivorous; but some inter-and intraspecific differences were observed. Generally, copepods consumed diatoms, dinoflagellates and microzooplankton. The omnivory index 'UC' (i.e., fatty acid unsaturation coefficient) varied from 0.2 to 0.6, which implied ingestion of phytoplankton. The different degree of selectivity on the same food items by the studied species was observed, and therefore, successful surviving strategy with minimal overlapping could be assumed. In total, the populations of the three studied copepod species grazed up to 2.15 g C m -2 day -1 and released up to 0.68 g C m -2 day -1 in faecal pellets. They consumed up to 50% of particulate organic carbon, or up to 85% of phytoplankton standing stock (in terms of Chl. a), and thus played a significant role in the transformation of particulate organic matter. Seasonal changes in abundance of the studied species depended mostly on water temperature in the early summer, but were also affected by food availability (Chl. a concentration) during the productive season.

Climate-driven changes in the phenology and composition of plankton affect ecosystem structure and function, but knowledge about such changes is limited by the scarcity of highquality, high-resolution, long-term monitoring data. Using a high-resolution observation series from the White Sea, spanning > 50 yr, we explored how water temperature and salinity influenced 2 key copepod species, Calanus glacialis and Pseudocalanus minutus. The results of the analysis depended critically on the temporal and life-stage resolution of the analysis. Copepod biomass was negatively correlated with salinity, but not correlated with temperature, when using annually aggregated data. However, salinity showed very small effects at a monthly resolution, failing to support a causal effect of salinity. On the other hand, temperature did show effects: in warm years, the biomass of C. glacialis increased earlier in spring and declined earlier in autumn. Analysis of stage-resolved data revealed a new level of complexity. The increase of biomass in spring at warmer temperatures mainly consisted of young life stages, whereas the decrease in autumn was mainly caused by reductions in older life stages. Temperature affected the phenology of several life stages of P. minutus, but not its total biomass, implying that climate effects on different life stages cancelled each other out. We argue that such climate-driven fluctuations in zooplankton phenology and age structure are likely to influence the role of the zooplankton as predators, competitors and prey, but that these effects of climate could remain unnoticed when using the coarser resolution of many sampling programs.KEY WORDS: Scale dependence · Copepods · Developmental stages · Temperature · Marine · White Sea · Phenology · Generalized additive modelling Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 468: [71][72][73][74][75][76][77][78][79][80][81][82][83] 2012 temperature−size rule), although the mechanisms causing such a shift are not clear. Changes in the structure of marine ecosystems can affect their function, which, in turn, may feed back on the structure. For example, shifts in the timing and size spectra of prey (copepods) influence the survival of juvenile cod (Munk 1997, Beaugrand et al. 2003), a key species in many North Atlantic shelf systems. In order to understand how climate affects the dynamics of marine ecosystems, it is therefore important to consider the associated changes in ecosystem structure, which requires data with sufficient resolution in space, time (season) and species' stage and size composition.In recent decades we have seen significant changes in the distribution and phenology of zooplankton. For example, the copepod biomass peak in the Central North Sea has advanced by 10 d in 45 yr (reviewed by Richardson 2008). In the Arctic, changes in the circulation and temperature of water and air, as well as changes in ice cover, have been shown to lead to increased primary production and altered zooplan...