Grazing during early spring in the Gulf of Aqaba and the northern Red Sea

Abstract

Zooplankton grazing on bacterio-and phytoplankton was studied in the Gulf of Aqaba and the Northern Red Sea during Meteor Cruise Me 44-2 in February-March 1999. Protozoan grazing on bacterioplankton and autotrophic ultraplankton was studied by the Landry dilution method. Microzooplankton grazing on phytoplankton > 6 µm was studied by incubation experiments in the presence and absence of microzooplankton. Mesozooplankton grazing was studied by measuring per capita clearance rates of individual zooplankton with radioactively labelled food organisms and estimating in situ rates from abundance values. Protozoan grazing rates on heterotrophic bacteria and on algae < 6 µm were high (bacteria: 0.7 to 1.1 d ), while grazing rates on Synechococcus spp. were surprisingly low and undetectable in some experiments. Mesozooplankton grazing was weak, cumulative grazing rates being ca. 2 orders of magnitude smaller than the grazing rates by protozoans. Among mesozooplankton, appendicularians specialised on smaller food items and calanoid copepods on larger ones. KEY WORDS: Phytoplankton · Protozoa · Bacteria · Zooplankton · Grazing · Red Sea · Gulf of Aqaba Resale or republication not permitted without written consent of the publisher

Lipid composition of tropical and subtropical copepod species of the genus Rhincalanus (Copepoda: Eucalanidae): a novel fatty acid and alcohol signature

“…Fatty alcohol profiles reported for Rhincalanus nasutus in Lee et al (1971a), Sommer et al (2002), andSchnack-Schiel et al (2008) were highly similar to those observed in the present study. Hexadecanol (16:0; 52 to 74% mass), 14:0 (15 to 19%), and octadecanol (18:0; 11 to 16%) made up almost the entire fatty alcohol fraction in those studies.…”

“…Total fatty acid or WE profiles from studies in the Red Sea and off the coast of southern California also showed an abundance of 16:1 and 18:1 fatty acids (Lee et al 1971a, Sommer et al 2002, Schnack-Schiel et al 2008. The main fatty acid contributors to the phospholipid fraction of R. nasutus collected off southern California included 20:5 (28.9%), 16:0 (19.4%), 22:6 (17.2%), 18:1 (11.5%), and 18:0 (7.4%) (Lee et al 1971a), which were the 5 major contributors in the present study as well.…”

“…Overall lipid content is high, with reported values ranging from 16 to 69% of dry weight (DW) (Lee & Hirota 1973, Morris & Hopkins 1983, Sommer et al 2002, Schnack-Schiel et al 2008. While this is not surprising for the high-latitude R. gigas, it is uncommon for tropical and subtropical species to accumulate large amounts of lipids, and for the accumulated lipids to be comprised of WEs (Lee & Hirota 1973).…”

“…All 4 Rhincalanus species accumulate wax esters (WEs) as the primary storage lipid (61 to 92% of total body lipid in adults), which are often present in a large oil sac (Lee et al 1971a, 2006, Lee & Hirota 1973, Sommer et al 2002, Schnack-Schiel et al 2008. Overall lipid content is high, with reported values ranging from 16 to 69% of dry weight (DW) (Lee & Hirota 1973, Morris & Hopkins 1983, Sommer et al 2002, Schnack-Schiel et al 2008.…”

Redescription of the poorly known calanoid copepod Pontella karachiensis Fazal-Ur-Rehman, 1973 from the Red Sea with notes on its feeding habits

“…, Klinker et al 1978, Sommer 2000, Sommer et al 2002, 2) phytoplankton of the northern Red Sea are constituted mainly of ultraphytoplankton (Lindell & Post 1995, Li et al 1998, Yahel et al 1998 which are too small (Ͻ8 mm) to be manipulated by its mouth parts, 3) this species may change its food items opportunistically as in some other pontellid species (Ohtsuka & Onbé 1991), and 4) the number of analyzed specimens was too small to detect vegetative foods in their guts.…”