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Abstract-The mean (ϮSE) depth-integrated gross production (P) of 2,600 Ϯ 271 mg O 2 m Ϫ2 d Ϫ1 derived from a compilation of data from nine cruises conducted between 1991-2000 in the subtropical NE Atlantic was found to be significantly lower (t-test, P ϭ 0.005, N ϭ 33) than the mean (ϮSE) community respiration (R) of 3,821. Two-thirds of the stations investigated were heterotrophic, and the P/R ratio of the communities tended to increase as P increased, such that communities where P Ͻ 3,000 mg O 2 m Ϫ2 d Ϫ1 tended to be heterotrophic. The tendency for R to exceed P (P/R Ͻ 1.0) was statistically significant (Wilcoxon ranked sign test, P Ͻ 0.05) in the upper and deep layers of the photic zone, with an overall balance between P and R at intermediate depths. These results provide evidence that the subtropical NE Atlantic is a heterotrophic ecosystem, where planktonic communities respire more organic carbon than they produce, thereby acting as net sources of CO 2 .

Gross oxygen production (GP), dark respiration (DR) and net community production (NCP) were studied for 16 mo in the euphotic layer of 3 stations through the coastal transitional zone of the southern Bay of Biscay, and related to hydrographic and nutrient conditions, phytoplankton biomass and C incorporation. Microbial O2 fluxes exhibited seasonal patterns linked to the seasonal cycle of water column stratification and mixing, with positive NCP during the spring, negative throughout the summer and close to zero in winter. This pattern was altered at coastal regions, where productive periods were linked to coastal upwelling, whereas in winter persistent net heterotrophy was measured, presumably in relation to increases in organic matter discharge of continental origin. The comparison of NCP with O2 anomaly and No3 concentration in the euphotic zone, the spatial and temporal scales studied and the prevalence of steady-state conditions offshore support the conclusion that the maintenance of summer heterotrophy in the region was based upon the consumption of the surplus of organic matter produced in spring. The uncoupling in the microbial auto-and heterotrophic metabolisms, based on the accumulation and delayed consumption of dissolved organic matter as a consequence of the processes controlling phytoplankton growth and microbial heterotrophic activity in temperate seas, would explain such a pattern. The close relationshp observed between the seasonal variability in NCP and the magnitude of spring net production and predictions derived from the seasonal cycles of O2 anomaly in middle latitudes and atmospheric O2 led us to conclude that the seasonal compensation of production and respiration processes is a characteristic of the dynamics of the pelagic ecosystem, at least in coastal temperate seas. The implications of this conclusion are of great relevance for the interpretation of new production and the estimation of the trophic status of the ocean from direct measurements of plankton net production.

[1] The southern Bay of Biscay (NW Spain) shows a very active hydrography due to the different origins of its Central Waters, the local modifications exerted on them by continental effects and the recurrence of mesoscale processes such as slope currents, upwellings and eddies. In order to assess the role of the different sources of variability we conducted a monthly series of CTD sampling in the central Cantabrian Sea along a coastal-oceanic transect, from 1993 to 2003. We analyzed the spatial variability of the hydrographic processes over different timescales. The thermohaline properties of Central Waters varied between those typical of the subpolar mode of the Eastern North Atlantic Central Water (ENACWsp) and a local mode, the Bay of Biscay Central Water (BBCW), though there has been a clear shift toward the BBCW prevalence in the last years. The Iberian Poleward Current (IPC) conveyed subtropical Central Waters (ENACWst) into the region almost every winter. This slope current may display a double-core structure during some extreme events. The upper layers of the ocean showed a long-term trend toward increasing temperature and decreasing salinity, and accordingly density was on the decrease. These patterns suggest an enhancement of the water column stratification. Coastal upwellings are an important source of inshore variability and counteract these long-term changes on the coast. However, their intensity seems to be decreasing and their seasonal pattern changing toward a general advancement of the upwelling-favorable season.

Abstract. Antarctic krill (Euphausia superba) and salps are major macroplankton contributors to Southern Ocean food webs and krill are also fished commercially. Managing this fishery sustainably, against a backdrop of rapid regional climate change, requires information on distribution and time trends. Many data on the abundance of both taxa have been obtained from net sampling surveys since 1926, but much of this is stored in national archives, sometimes only in notebooks. In order to make these important data accessible we have collated available abundance data (numerical density, no. m−2) of postlarval E. superba and salps (combined aggregate and solitary stages and species) into a central database, KRILLBASE, together with environmental information, standardisation and metadata. The aim is to provide a temporal-spatial data resource to support a variety of research such as biogeochemistry, autecology, higher predator foraging and food web modelling in addition to fisheries management and conservation. Previous versions of KRILLBASE have led to a series of papers since 2004 which illustrate some of the potential uses of this database. With increasing numbers of requests for these data we here provide an updated version of KRILLBASE that contains data from 15,194 net hauls, including 12,758 with krill abundance data and 9,726 with salp abundance data. These data were collected by 10 nations and span 56 seasons in two epochs (1926–1939 and 1976–2016). Here, we illustrate the seasonal, inter-annual, regional and depth coverage of sampling, and provide both circumpolar- and regional-scale distribution maps. Krill abundance data have been standardised to accommodate variation in sampling methods, and we have presented these as well as the raw data. Information is provided on how to screen, interpret and use KRILLBASE to reduce artefacts in interpretation, with contact points for the main data providers.