The seasonal abundance and production of Oithona nana (Copepoda:Cyclopoida) in Southampton Water

Abstract

Recent studies indicate that Oithona spp. contribute significantly to total copepod biomass. Little is known, however, about their ecological significance, particularly in the case of the estuarine Oithona nana. A study comprising three sites within Southampton Water was conducted to evaluate the late-stage copepodite/adult (stages IV-VI) O. nana community, using 120-mm mesh nets. Although present throughout the estuary, there was a striking spatial gradient with O. nana most common in the upper estuary. A clear seasonal pattern was observed with O. nana as the most abundant copepod species from late summer until early winter. It comprised 61% of all copepods recorded, with a biomass of 757.22 mg C m -3 . Production estimates of O. nana were derived from the 'instantaneous-growth' approach, using appropriate growth equations. The estimated production of O. nana ranged from 1.50 mg C m -3 year -1 within the lower estuary to 146.77 mg C m -3 year -1 in the upper estuary. In the upper estuary, this compares with production rates of 187.47 mg C m -3 year -1 for all Acartia congeners (excluding nauplii), the most common calanoid genus. Throughout the estuary, O. nana annual production represented 18% of total copepod production clearly indicating that, at least in the upper estuary, O. nana production may be directly comparable with calanoid production.

Spatial variations in reproductive characteristics of the small copepod Oithona similis in the Barents Sea

“…Spatial trends in O. similis biomass were associated strongly with water temperature (Table 3). Similar patterns have been observed for O. similis in the southern and eastern Barents Sea (Dvoretsky 2008, Dvoretsky & Dvoretsky 2009a, O. davisae in Fukuyama Harbor (the Inland Sea of Japan) (Uye & Sano 1998), O. nana in Southampton Water (Williams & Muxagata 2006) and Oithona spp. in the Irminger Sea (Castellani et al 2007).…”

“…production (P) estimated from 63 µm mesh size net sampler probes has been found to vary between 13.1 and 153.6 µgC m -3 d -1 in 0 to 120 m layer during summer in the Irminger Sea area (Castellani et al 2007). In the Inland Sea of Japan in July-August, O. davisae production rate was 2 to 10.9 mgC m ) (Williams & Muxagata 2006). We suggest that food conditions had a greater effect in determining production than hydrological conditions as we found no significant correlations between total production and water temperature and salinity (Table 4).…”

“…The secondary production of females (SP F , µg C m ), g is growth rate; g M was assumed as equal to SEPR (Sabatini & Kiørboe 1994, Williams & Muxagata 2006) and g C is the average specific growth rate over copepodite stages estimated from equations (Hirst & Bunker 2003): (7) where W C is the mean carbon weight of CIV or CV copepodites (µg ind.…”

The importance of vertical habitat gradients on zooplankton distribution in an enclosed marine environment (South Adriatic Sea)

“…Over recent decades, reducing the net mesh size highlighted the importance of the genus Oithona in marine ecosystems, and also their relative importance compared to calanoid copepods (Gallienne & Robins 2001;Hansen et al 2004;Turner 2004). Due to its wide tolerance to temperature and salinity and opportunistic diet (Lampitt & Gamble 1982;Gonzáles & Smetacek 1994;Nakamura & Turner 1997;Williams & Muxagata 2006), O. nana and O. similis are well adapted for the utilization of food resources in stratified environments. Regardless of similar abundance patterns of both oithonidcyclopoid species, a different seasonal vertical distribution pattern was observed, and O. similis has been found mostly in deeper layers.…”

Development, growth, and reproduction of the cyclopoid copepod Limnoithona tetraspina in the upper San Francisco Estuary

“…Oithona species can be abundant in estuaries, but generally not at low salinity (Uye & Sano 1995, Johnson & Allen 2005, Williams & Muxagata 2006. The genus Limnoithona consists of 2 estuarine species that are native to China, both of which have been introduced to the San Francisco Estuary (SFE), USA (Orsi & Ohtsuka 1999).…”