Seasonal occurrence and hatching of calanoid eggs in sediments of the northern Baltic Sea

Abstract

The seasonal occurrence and hatching of benthic eggs of calanoid copepods were studied for 1 yr in the surface sediments at 2 sites (a 33 m deep archipelago area and a 42 m deep site in an enclosed bay) off the SW coast of Finland, northern Baltic Sea. Eggs were abundant at both sites (up to 4 and 6 X 106 eggs m-2). At the archipelago site, most eggs belonged to Acartia bifilosa and A. tonsa; at the bay site, eggs of Eurytemora affinis and Acartia spp. occurred. At the archipelago site, the egg numbers in the surface sediment followed closely the seasonal abundance of the planktonic Acartia spp. females. The eggs collected from the sediment were Incubated at temperatures corresponding to the in situ bottom temperatures. Hatching of the A. bifilosa eggs occurred throughout the year, but it was most intensive in autumn when water stratification broke and the deep water warmed up to 13°C. It is suggested that a large number of the A. bifilosa eggs sink to the bottom prior to hatching m shallow coastal areas of the Baltic Sea. Hatching of the benthic eggs occurs throughout the year and the rate of naupliar emergence from the sediments depends on benthc condtions and processes (e.g. temperature, sediment resuspension and bioturbation). At the bay site, where the surface water layer was hydrographically separated from the deep water, the coupling between the benthic egg abundance and the planktonic populations was not so obvious. The dominant species E. affinis carries its eggs in an egg sac unhl hatching, and probably only the diapause eggs, which are produced in autumn, fall to the bottom. A. tonsa was abundant in the water column at both study sites in autumn, even outnumbering other Acartia spp. in some samples. The eggs of the species only hatched in autumn, when the incubations were conducted at 10 to 13°C. It is probable that A. tonsa spends most of the year as benthic resting eggs In the northern Baltic Sea. In contrast, A bifilosa and E. affinis occurred in the plankton in winter at both study sites, though in low concentrations. They thus have 2 possible sources of recruitment when conditions are again favourable for population growth in spring: hatching of benthc eggs and reproduction by the overwintering population.

Environmental cues and constraints affecting the seasonality of dominant calanoid copepods in brackish, coastal waters: a case study of Acartia, Temora and Eurytemora species in the south-west Baltic

“…Work on E. affinis at different sites suggests the production of eggs that did not rapidly hatch were related to short day lengths, cold temperatures and high copepod population densities (Ban 1992;Flinkman et al 1994;Katajisto 1996;Andersen and Nielsen 1997;Katajisto et al 1998;Roman et al 2001). For example, Ban (1992) collected nauplii of E. affinis in lake Ohnuma, Japan, during late autumn (November) and reared them in the laboratory under spring conditions (15°C, 12 h).…”

First evidences of <i>Acartia bifilosa</i> resting eggs in sediments of the Urdaibai estuary (Bay of Biscay): abundance and hatching success

“…Uye, 1980;Belmonte and Puce, 1994;Marcus, 1995;Norrbin, 1996;Belmonte, 1997;Guerrero and Rodríguez, 1998), including Acartia bifilosa (e.g. Viitasalo, 1992b;Katajisto, 1996, Katajisto et al, 1998Castro-Longoria and Williams, 1999;Chinnery and Williams, 2003). This species shows a great adaptability to environments with different salinity, from the mesohaline waters of the Baltic Sea (Viitasalo, 1992a) to the polyhaline and mesohaline regions of large estuaries, such as the Severn (Collins and Williams, 1981), the Gironde (Castel, 1981), the Forth (Taylor, 1987) and the Ems (Baretta and Malschaert, 1988), and some shallow lagoons (Lam-Hoai, 1985).…”

“…the water column for a part of the year (Uye, 1985;Marcus, 1989) or those that undergo strong seasonal fluctuations (Katajisto et al, 1998). In planktonic organisms, hatching from resting eggs enables a multiple acceleration of population increase during the beginning of the development of a population with periodical re-establishment from this phase (Boero, 1994;Arbaciauskas and Gasiunaité, 1996), and is of great importance in explaining species fluctuations in space and time (Giangrande et al, 1994) and benthic-pelagic coupling (Boero et al, 1996;Marcus and Boero, 1998).…”

Effects of photoperiod on egg production inEurytemora affinisPoppe, 1880 (Copepoda: Calanoida) from the Seine Estuary (France)

“…In contrast to what is observed in Japan, where the species is known to disappear entirely from the water column in winter (Ban & Minoda 1989), E. affinis is known to reproduce throughout the year in many estuaries of the northern hemisphere (Cronin et al 1962;Jeffries 1962;Haertel et al 1969;De Pauw 1973;Soltanpour-Gargari & Wellershaus 1985;Baretta & Malschaert 1988). For these populations, the production of diapausing eggs was revealed only after extraction of eggs from sediment layers (Madhupratap et al 1996;Katajisto et al 1998;Albertsson & Leonardsson 2000). In the Seine estuary, diapausing eggs were also found ) and we assessed here the effect of photoperiod on diapausing egg production in E. affinis.…”

“…These results suggest that the diapausing egg production of E. affinis in these latitudes is not essential for winter survival since population reproduction with subitaneous eggs is possible in the water column throughout the year. The planktonic E. affinis population could be replaced after the winter period from two sources, as shown in the Baltic Sea (Katajisto et al 1998): (1) hatching of benthic resting eggs; (2) hatching of eggs produced by females that have survived the winter.…”