Untitled

Abstract

SUMMARY: Elemental (C, H, O, N, Si, P) and biochemical composition (proteins, carbohydrates, lipids, phosphorus compounds, chlorophyll and opal) in particulate organic matter, diatoms, other autotrophs, heterotrophs and detritus from natural plankton were established simultaneously by measuring relatively few components. Using standard techniques in marine chemistry on board ship, it is possible to infer a great deal about the composition and condition of the plankton. In addition, the organic matter content in terms of cell volume was determined for each group of plankton. Variation of chemical composition with depth was also considered. The ratio carbohydrates/lipids (Cbh/Lip) was used as an indicator of the chemical quality of the plankton.

The biogeochemistry of nutrients, dissolved oxygen and chlorophyll <em>a</em> in the Catalan Sea (NW Mediterranean Sea)

“…It is unlikely that the decrease in nitrate from this maximum to the bottom of the basin (Fig. 3) is due to denitrifi- cation, since this process requires lower oxygen concentrations than those measured at deep Catalan Sea waters (Riley 1971, Millero 1996. Phosphate and nitrate concentrations remain approximately constant below the maximum in intermediate waters to the bottom of the basin, indicating that all the labile phosphate and nitrate contained in sinking organic matter have already been remineralized.…”

“…A larger chlorophyll concentration in diatoms compared with cultured dinoflagellates and other autotrophic organisms in natural samples has actually been suggested (e.g. Ríos et al 1998). Another adaptation that would lead to higher cellular N:P ratios is the preferential synthesis of N-rich substitute lipids in response to P limitation, as found in the Adriatic Sea (Ivančić et al 2012).…”

“…Coincident with the DCM, the primary nitrite maximum (PNM) is found (Estrada et al 1993, Bahamón andCruzado 2003). The coincidence has been explained by the phytoplankton excretion of nitrite as a result of the incomplete nitrate assimilation for cellular requirements (Riley 1971), for example because of the low light intensities (e.g. Blasco 1971, Olson 1981.…”

“…In addition, the Mediterranean Sea is characterized by having almost permanently stratified water columns, though their intensity throughout the year is variable. In stratified water columns the nutrients regenerated in deep waters are prevented from reentering the euphotic zone, where nutrient concentrations are low due to their consumption by osmotrophic organisms (Riley 1971). Consequently, the Mediterranean Sea is an oligotrophic sea, with low levels of Chl a in surface waters, so low levels of primary production are expected.…”

Cannonball jellyfish digestion: an insight into the lipolytic enzymes of the digestive system

“…This research studied wild individuals; thus, differences in protein concentration and lipase/esterase activity among individuals could have been the result of many factors, such as size, reproductive stage, and feeding (Carvalho-Saucedo et al, 2009;Lucas, 1994). Plankton (microalgae, fish eggs, and larvae) is crucial for cnidarian feeding (Orejas et al, 2002;Purcell & Arai, 2001); its biochemical composition varies, but lipids are always present (Ríos et al, 1998).…”