Adaptation of marine plankton to environmental stress by glycolipid accumulation

Abstract

A systematic investigation of non-phosphorus containing glycolipids (GL) was conducted in the northern Adriatic Sea during two years at two stations with different nutrient loads. GL concentration varied both spatially and temporally, with values of 1.1-21.5 μg/L and 0.4-44.7 μg/L in the particulate and the dissolved fraction, respectively. The highest concentrations were measured during summer in surface waters and at the more oligotrophic station, where GL yields (% of total lipids) were often higher than 20% and 50% in the particulate and dissolved fractions, respectively. To obtain more insight into factors governing GL accumulation autotrophic plankton community structure (pico-, nano- and microplankton fractions), chlorophyll a, heterotrophic bacteria and nutrient concentrations were measured together with hydrographic parameters and sunlight intensity. During the investigated period smaller autotrophic plankton cells (pico- and followed by nanoplankton) prevailed in abundance over larger cells (microplankton), which were found in large numbers in freshened surface samples. Several major findings resulted from the study. Firstly, during PO4 limitation, particularly at the oligotrophic station, enhanced glycolipid instead of phospholipid accumulation takes place, representing an effective phosphate-conserving mechanism. Secondly, results suggest that at seawater temperatures >19 °C autotrophic plankton considerably accumulate GL, probably to achieve thermal stability. Thirdly, high sunlight intensities seem to influence increased GL accumulation; GL possibly plays a role in cell mechanisms that prevent/mitigate photooxidation. And finally, substantial accumulation of GL detected in the dissolved fraction could be related to the fact that GL do not contain biologically relevant elements, like phosphorus, which makes them an unattractive substrate for enzyme activity. Therefore, substantial portion of CO2 could be removed from the atmosphere in P-limited regions during summer via its capture by plankton and conversion to GL.

Alkaline phosphatase activity related to phosphorus stress of microphytoplankton in different trophic conditions

“…From a variety of possible phytoplankton strategies we propose here 4 of them (Fig. 8) that in the light of results presented herein, authors' experiences and earlier work (Gašparović et al, 2013;Godrijan et al, 2013;Ivančić et al, 2004Ivančić et al, , 2012Viličić et al, 2013) appear to be the most plausible.…”

Factors influencing particulate lipid production in the East Atlantic Ocean

“…Replacement of membrane phospholipids by non-phosphorus containing GL represents an effective phosphate-conserving mechanism in many organisms during phosphate limitation, including photosynthetic bacteria, algae and higher plants (e.g., Benning et al, 1995;Andersson et al, 2003). Enhanced synthesis and accumulation of glycolipids was found during nutrient depletion in a mesotrophic coastal sea (Frka et al, 2011;Gašparović et al, 2013). The high concentrations of glycolipids found in the surface and DCM layers, the increase of GL versus PG and the relation of GL with smaller cell sized phytoplankton were an indication of the oligotrophic conditions even in the DCM layer where light limitation may also affect the lipid production.…”

Report of the Croatian Committee of Geodesy and Geophysics on activities carried out between 2011 and 2014

“…Collaboration with chemists, biologists, fishery scientists and geologists was established, resulting in number of interdisciplinary papers dealing with climate and circulation impact on the ecosystem variability (Skejić et al, 2014;Sikora et al, 2014;Gašparović et al, 2013;Gordijan et al, 2013;Viličić et al, 2013;Zorica et al, 2013;Carić et al, 2012;Kršinić and Grbec, 2012;Morović et al, 2012;Vidjak et al, 2012;Viličić et al, 2011). The laboratory of Physical Oceanography at the Institute of Oceanography and Fisheries, Split, in cooperation with the State Hydrometeorology Institute of Croatia, has established a virtual laboratory (http://www.izor.hr/web/ guest/virtual-laboratory) in order to study interactions between climate change and the marine ecosystem through monitoring of a variety of physical parameters in the atmosphere, the sea and at the air-sea interface.…”