Seasonal abundance and distribution of Caridea larvae in Isafjord-deep, north-west Iceland

The abundance and distribution of Candea larvae was studiedin Ísafjord-deep, north-west Iceland, at approximatelymonthly intervals from February 1987 to February 1988 Zooplanktonsampling was made at nine stations along the length of the fjord,while temperature and chlorophyll a measurements from one ofthe stations are also presented Larvae of six species occurredin the samples, Eualus pusiolus and Pandalus borealis were mostnumerous, constituting 62 8 and 25 9% of the larvae respectively.The other species were, in declining order of abundance, Pandalusmontagui, Spirontocaris spp. (S spinus and s lilljeborgii) andSabinea septemcarinata. Eualus pusiolus was of highest abundancein the outer and middle parts of the fjord, while P.borealiswas most common in the middle and inner parts The onset of hatchingof all species in April–May appeared closely linked tothe phytoplankton spring bloom, while the temperature in thefjord was by then near the annual low (2–3°C). Exceptfor E pusiolus, of which a small part of the population produceda second brood during the summer, most of the larvae had disappearedfrom the plankton by the middle of August The monthly carapacegrowth of P.borealis larvae during the summer months was estimatedto be 1.0 mm.     

New and historical records of the ocean sunfish Mola mola in Icelandic waters

The ocean sunfish Mola mola is considered to be globally distributed in both temperate and tropical waters, but there are many gaps in the knowledge of this species' distribution. A total of 31 records of M. mola from Icelandic waters, dating from 1845 to 2014, are presented and georeferenced. An increase in the number of records at the beginning of this century and particularly in 2012, is suggested to be a consequence of both an increase in ocean temperature on the Icelandic shelf and changes in large scale temperature variations in the North Atlantic Ocean.     

Records and life history of Praunus flexuosus (Crustacea: Mysidacea) in Icelandic waters

Since its fust record in Icelandic waters in 1970, Praunus flexuosushas been found to be very common in the littoral zone of theAtlantic water at the south-west coast of Iceland. It seemspossible that P. flexuosus has only recently been introducedinto Icelandic waters. The life history of P. flexuosus hasbeen followed in Skerjafjord, near Reykjavik, in 1985–1986.The animals have a one-year life span. The females, some ofwhich appear to produce three broods, breed mainly during June–August.Breeding females ranged in length from 18.7 to 25.7 mm and thelargest brood was 72 eggs. The incubation time at c. 11°Cwas estimated to be 25 days. The daily growth rate of juvenileswas estimated to be 0.16 mm in July–August and 0.05–0.07mm in September–October. No growth occurred during thewinter months of October–March.     

Seasonal cycle of zooplankton southwest of Iceland

Seasonal variations in biomass, abundance and species compositionof zooplankton in relation to environmental parameters and chlorophylla were studied in both the Coastal water [salinity] (S) <35.0     

Seasonal variations in biomass, abundance and composition of zooplankton in the subarctic waters north of Iceland

The seasonal variations in biomass, abundance and species composition of zooplankton in relation to hydrography and chlorophyll a were studied in the subarctic waters north of Iceland. The sampling was carried out at approximately monthly intervals from February 1993 to February 1994 at eight stations arranged along a transect extending from 66°16′N–18°50′W to 68°00′N–18°50′W. The mean temperature at 50 m depth showed a clear seasonal pattern, with lowest water temperatures in February (∼1.1°C) and the highest in July (∼5.4°C). The spring growth of the phytoplankton began in late March and culminated during mid-April (∼7.0 mg Chl a m⁻³). Both the biomass and the abundance of total zooplankton were low during the winter and peaked once during the summer in late May (∼4 g m⁻² and ∼38,000 individuals m⁻²). A total of 42 species and taxonomic groups were identified in the samples. Eight taxa contributed ∼90% of the total zooplankton number. Of these Calanus finmarchicus was by far the most abundant species (∼60% of the total zooplankton). Less important groups were ophiuroid larvae (∼9%), Pseudocalanus spp. (∼8%), Metridia longa (∼4%), C. hyperboreus (∼3%), Acartia longiremis (∼2%), chaetognaths (∼2%) and euphausiid larvae (∼2%). The dominant copepods showed two main patterns in seasonal abundance: C. finmarchicus, C. hyperboreus and C. glacialis had one annual peak in numbers in late May, while Pseudocalanus spp., M. longa and A. longiremis showed two maxima during the summer (July) and autumn (October/November). Ophiuroid larvae and chaetognaths (mainly Sagitta elegans) peaked during the middle of July, while the number of euphausiid eggs and larvae was greatest from May to July. The succession in population structure of C. finmarchicus indicated its main spawning to be in April and May, coincident with the phytoplankton spring bloom. A minor spawning was also observed sometime between August and October. However, the offspring from this second spawning contributed only insignificantly to the overwintering stock of C. finmarchicus. Received: 12 September 1997 / Accepted: 1 March 1998     

Seasonal variations in abundance, development and vertical distribution of Calanus finmarchicus, C. hyperboreus and C. glacialis in the East Icelandic Current

The seasonal variation in abundance and development of Calanusfinmarchicus, Calanus hyperboreus and Calanus glacialis in relationto hydrography and chlorophyll (Chl) a was studied in the Arcticwaters of the East Icelandic Current to the north-east of Icelandfrom March 1995 to February 1996. The sampling was carried outat approximately monthly intervals on a transect of five stationsextending from 67°00'N, 13°55'W to 68°00'N, 12°40'W.In April, May and June, vertical distribution was also investigated.Spring warming of the surface waters began in May, with maximumtemperatures recorded in August (~5°C, mean for uppermost50 m). Below 75 m, temperature remained at <0°C throughoutthe year. The spring bloom of phytoplankton started in earlyMay and the highest Chl a concentrations were measured duringlate May to early June (~1 mg Chl a m^-3). Calanus finmarchicusdominated in terms of numbers (~75%), while C. hyperboreus dominatedbiomass (~76%). Calanus glacialis occurred only in low numbers(~1%) and was only a small portion of biomass (~0.7%). The abundanceof all species was low during the winter and peaked once duringsummer: C. finmarchicus in July (~16 000 ind. m^-2) and C. glacialisand C. hyperboreus in June (~370 and ~7700 ind. m^-2, respectively).The biomass of C. finmarchicus had two maxima, in April (~1.9g m^-2) and July (~1.5 g m^-2), while C. hyperboreus peaked inJune (~12.3 g m^-2). Calanus finmarchicus was estimated to spawnin early May at about the start of the spring bloom, while C.hyperboreus spawned prior to the spring bloom, in late Februaryto early March. On the basis of copepod stage distribution,C. finmarchicus was considered to have a 1-year life cycle andC. hyperboreus at least a 2-year life cycle.     

Abundance and distribution of early life stages of krill around Iceland during spring

Abundance, distribution and development of early life stages of krill (eggs, nauplii, calyptopes and furciliae) around Iceland were studied during the latter half of May 2013. Multivariate analyses were used to examine the relationships between water mass characteristics and phytoplankton spring bloom dynamics and distribution of krill. The results show that krill eggs, nauplii and calyptopes were most abundant over the shelf edges off the southwest and east coasts, while furciliae were most abundant on the shelf off the southwest coast. Meganyctiphanes norvegica and Thysanoessa longicaudata larvae were found mainly in the southwest, while T. inermis larvae were found in highest numbers on the east coast. Redundancy analysis showed that phytoplankton biomass, temperature and bottom depth explained 41% of the distribution pattern of early ontogenetic krill stages. In areas where krill eggs and larvae were most abundant (off the southwest coast), the phytoplankton spring bloom was in an advanced state, and the phytoplankton biomass and temperature were particularly high.