Semi-Intrinsic Luminescence in Marine Organisms

Light emission is widespread in the oceans, with over three quarters of all observed marine species exhibiting bioluminescence. Several organisms such as the copepod Metridia pacifica and the ostracod Vargula hilgendorfii have been proven to synthesise their luciferin and luciferase to facilitate light emission. However, many luminescent species lack the capability to do this and instead it is possible that they acquire some of the components for their luminescence through predation or filter feeding on organisms that produce luciferins or precursors to these molecules. This has resulted in many organisms using certain luciferins, such as coelenterazine, as their substrate without possessing a clear mechanism to synthesise these. This chapter will review several examples of these semi-intrinsic luminescent systems and how the substrates and enzymes can be obtained for these reactions. Moreover, it will look at why particular luciferins, such as coelenterazine, are more widespread and utilised in this manner compared to other substrates.

Composition and structure of plankton communities in the Bering Sea

On the data of long-term surveys, mean biomass of plankton in the epipelagic layer of the Bering Sea is evaluated as 821.3 mg/m3 (1058.2 mg/m3 in shelf areas and 760.6 mg/m3 in the deep-water areas) and the stock as 245.1•106 t WW (64.4 • 106 t over the shelf and 180.7 • 106 t in the deep-water sea). By taxa, the average annual portions are: 55.1 % for copepods, 26.3 % for arrowworms, 10.8 % for euphausiids, 3.2 % for medusas, and 2.9 % for amphipods. The dominant species are the arrowworm Sagitta elegans (26.3 %) and the copepod Eucalanus bungii (19.7 %); other mass species are: large-sized copepods Neocalanus cristatus (10.4 %), Neocalanus plumchrus + Neocalanus flemingeri (7.8 %) and Calanus glacialis + Calanus marshallae (5.1 %), euphausiids Thysanoessa raschii (3.5 %) and Thysanoessa longipes (3.4 %), small-sized copepods Metridia pacifica (3.5 %) and Oithona similis (3.5 %), medusa Aglantha digitale (3.2 %).

Seasonal appearance of expatriated boreal copepods in the Oyashio–Kuroshio mixed region

Kobari, T., Moku, M., and Takahashi, K. 2008. Seasonal appearance of expatriated boreal copepods in the Oyashio–Kuroshio mixed region. – ICES Journal of Marine Science, 65: 469–476. Seasonal changes in abundance, biomass, and community structure of ontogenetically migrating copepods were investigated using monthly zooplankton samples from the Oyashio–Kuroshio mixed region (OKMR) to evaluate impacts of the copepod community expatriated from more northerly waters on carbon flow in southern areas. The copepod community comprised more than half the total zooplankton biomass and exhibited seasonal fluctuations, although they were minor components in terms of abundance. The ontogenetic migrants increased their abundance and biomass during May–July when Oyashio waters dominated at the surface. They were almost absent from 0 to 150 m during August to December. Predominant species were Eucalanus bungii and Metridia pacifica for abundance and Neocalanus cristatus for biomass. Seasonal changes in their abundance and stage composition indicated that surface development, dormancy, and reproduction were comparable in schedule with those reported in the Oyashio region. We suggest that the ontogenetically migrating copepods appearing in this area are populations transported with a southward Oyashio intrusion during surface development seasons, then by both downward migration and advection of dormant populations in the submerging Oyashio flow. We discuss impacts of the expatriated copepods on food availability for mesopelagic fish in the OKMR.