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.

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