Physiological energetics of the thick shell mussel Mytilus coruscus exposed to seawater acidification and thermal stress

Anthropogenic CO2 emissions have caused seawater temperature elevation and ocean acidification. In view of both phenomena are occurring simultaneously, their combined effects on marine species must be experimentally evaluated. The purpose of this study was to estimate the combined effects of seawater acidification and temperature increase on the energy budget of the thick shell mussel Mytilus coruscus. Juvenile mussels were exposed to six combined treatments with three pH levels (8.1, 7.7 and 7.3) * two temperatures (25 °C and 30 °C) for 14 d. We found that clearance rates (CRs), food absorption efficiencies (AEs), respiration rates (RRs), ammonium excretion rates (ER), scope for growth (SFG) and O:N ratios were significantly reduced by elevated temperature sometimes during the whole experiments. Low pH showed significant negative effects on RR and ER, and significantly increased O:N ratios, but showed almost no effects on CR, AE and SFG of M. coruscus. Nevertheless, their interactive effects were observed in RR, ER and O:N ratios. PCA revealed positive relationships among most physiological indicators, especially between SFG and CR under normal temperatures compared to high temperatures. PCA also showed that the high RR was closely correlated to an increasing ER with increasing pH levels. These results suggest that physiological energetics of juvenile M. coruscus are able to acclimate to CO2 acidification with a little physiological effect, but not increased temperatures. Therefore, the negative effects of a temperature increase could potentially impact the ecophysiological responses of M. coruscus and have significant ecological consequences, mainly in those habitats where this species is dominant in terms of abundance and biomass.

The distribution of meiofauna in surface sediments of the Fladen Ground, North Sea

A general study of structure, biomass, and dynamic estimates on meiofauna was carried out during PREFLEX (1975) and FLEX (1976), in 117- 141 m water depth. On the basis of these data an attempt was made to estimate meiofauna production, and this is discussed in relation to the energy input from the spring phytoplankton bloom. Sampling was performed at five stations, but only the stations 1, 4, and 5 were covered by a complete series from August 1975 to July 1976. At each station, from four replicate box core samples, two were withdrawn to study the abundance, distribution, and biomass of meiofauna, the content of chloroplastic pigment equivalents (CPE), and chemical and grain size analyses. At all stations grain size fell in the range of fine sand having median diameters (MD) of < 125 µm. From station 1 to 5 an increase in MD was observed. Highest values of CPE (7.81 µg m l**-1) and organic matter (4.7 %) were obtained in June and July (1976)/ August (1975), respectively. Meiofauna abundance was fairly uniform at all stations examined. Station 1 displayed maximal numbers during the whole investigation period. The abundance per 100 cm**2 varied between 15,550 and 34,900 organisms. All meiofauna studied both in total and as separate taxa showed annual cycles of abundance. Low abundance values were recorded during early summer, and maximum values during winter. High numbers of Foraminifera were obtained for August 1975 (9,460 per 100 cm**2) and July 1976 (9,710 per 100 cm**2). From December to June the values decreased from 3,280 to 1,030 per 100 cm**2. At station 1 maximum values of meiofauna biomass were recorded ranging from 1.5 to 2.7 g DWT m**-2. The mean meiofauna dry weight amounted to 2.1 g DWT m**-2. Based on minimum production, the P/B ratio for the area of station 1 might have a mean of 1.4. Taking into consideration generation times we believe that a turnover ratio of 2 is a conservative value for the Fladen Ground meiofauna. The annual production would amount to 4.2 g DWT m**-2 yr**-1. This is 27.5 % of the energy supply during the spring phytoplankton bloom, which is channelled into the meiofauna. The hypothesis is put forward that the energetic strategy of deep offshore meiofauna differs distinctively from that of shallow inshore meiofauna. While the shallow inshore meiofauna show a relatively fast response to organic matter input, the deep offshore meiofauna reacts much more slowly, the food energy consumption seems to be spread out over a longer period.

Diagenetic alteration of organic matter in DSDP Leg 57 Holes

I analyzed Leg 57 sediments organogeochemically and spectroscopically. Organic carbon and extractable organic matter prevail from the Pliocene to the Miocene. Humic acids occur widely from the Pleistocene to the lower Miocene and one portion of the Oligocene. The absence of humic acids in Oligocene and Cretaceous samples suggests that humic acids had changed to kerogen. Visible spectroscopic data reveal that humic acids in this study have a low degree of condensed aromatic-ring system, which is a feature of anaerobic conditions during deposition, and that chlorophyll derivatives that had at first combined with humic acids moved to the solvent- soluble fraction during diagenesis. The elemental compositions of humic acids show high H/C and O/C ratios, which seem appropriate to a stage before transformation to kerogen. The relation between the linewidths and g-values on the electron spin resonance data indicates that the free radicals in humic acids are quite different from those in kerogen. The low spin concentrations of kerogen and the yields of humic acids up to the lower Miocene demonstrate that organic matter in these sediments is immature. The foregoing indicate the necessity to isolate humic acids even in ancient rocks in the study of kerogen.

Abundance and biomass of mesozooplankton in the Levantine Basin during the Bilim 2 cruise in April 2008

The Sesame dataset contains mesozooplankton data collected during April 2008 in the Levantine Basin (between 33.20 and 36.50 N latitude and between 30.99 and 31.008 E longitude). Mesozooplankton samples were collected by using a WP-2 closing net with 200 µm mesh size during day hours (07:00-18:00). Samples were taken from 0-50, 50-100, 100-200 m layers at 5 stations in Levantine Basin The dataset includes samples analyzed for mesozooplankton species composition, abundance and total mesozooplankton biomass. Sampling volume was estimated by multiplying the mouth area with the wire length. Sampling biomass was measured by weighing filters and then determined by sampling volume. The samples were sieved sequentially through meshes of 500 and 200 micron to separate the mesozooplankton into size fractions. The entire sample (1/2) or an aliquot of the taxon-specific mesozooplankton abundance and the total abundance of the mesozooplankton were was analyzed under the binocular microscope. Minimum 500 individuals of mesozooplankton were identified and numerated at higher taxonomic level. Taxonomic identification was done at the METU- Institute of Marine Sciences by Alexandra Gubanova,Tuba Terbiyik using the relevant taxonomic literatures. Mesozooplankton abundance and biomass were estimated by Zahit Uysal and Yesim Ak.

Organic geochemistry of Cretaceous black shales at DSDP Hole 75-530A

Five-hundred ten meters of Cretaceous sediments were drilled north of the Walvis escarpment in Hole 530A during Leg 75. An immature stage of evolution for organic matter can be assigned to all the samples studied. Black shales are interbedded with red and green claystone in the bottom sedimentary unit, Unit 8, which is of Coniacian to late Albian age. The richest organic carbon contents and petroleum potentials occur in the black shales. Detrital organic matter is present throughout the various members of a sequence, mixed with largely oxidized organic matter in the gray and green claystone or marlstone members on both sides. Detrital organic matter also characterizes the black streaks observed in the claystones. Vertical discontinuities in organic matter distribution are assigned to slumping. Several types of black shales can be identified, according to their content of detrital organic matter, the more detrital black levels corresponding to the Albian-Cenomanian period. Cyclic variations of organic matter observed for a sequence can occur for a set of sequences and even for some consecutive sets of sequences. Climatic factors are proposed to account for the cyclic sedimentation and distribution of organic matter for every sequence that includes a black bed.