Extreme conditions reduce hatching success of green turtles (Chelonia mydas L.) at Karan Island, the major nesting site in the Arabian Gulf.

Survival in the early life stages is a major factor determining the growth and stability of wildlife populations. For sea turtles, nest location must provide favorable conditions to support embryonic development. Hatching success and incubation environment of green turtle eggs were examined in July 2019 at Karan Island, a major nesting site for the species in the Arabian Gulf. Mean hatching success averaged at 38.8 % (range = 2.5-75.0 %, n = 14). Eggs that suffered early embryonic death (EED) and late embryonic death (LED) represented 19.8 % (range: 3.3-64.2 %) and 41.4 % (range: 4.8-92.6 %) of the clutch on average, respectively. Nest sand was either coarse (0.5-1 mm: mean 44.8 %, range = 30.4-56.9 % by dry weight, n = 14) or medium (0.25-0.5 mm: mean 33.6 %, range = 12.0-45.5 % by dry weight, n = 14). Mean sand moisture (4.0 %, range = 3.2-4.9 %, n = 14) was at the lower margin for successful development. Hatching success was significantly higher in clutches with sand salinity <1500 EC.uS/cm (n = 5) than those above 2500 EC.uS/cm (n = 5). Mean clutch temperatures at 1200 h increased by an average of 5.4 °C during the 50-d post-oviposition from 31.2 °C to 36.6 °C. Embryos experienced lethally high temperatures in addition to impacts of other environmental factors (salinity, moisture, sand grain size), which was related to reduced hatching success. Conservation initiatives must consider the synergistic influence of the above parameters in formulating strategies to improve the overall resilience of the green turtle population in the Arabian Gulf to anthropogenic and climate change-related stressors.

Interaction of free-living marine nematodes in the artificial mangrove environment (Southeast Coast of India).

Free-living marine nematode diversity was analyzed between Avicennia marina and Rhizophora mucronata mangrove covers of the Vellar Estuary (southeast coast of India). A total of 4,976 specimens of free-living marine nematodes were collected in 56 species. Comparatively, a higher species richness was obtained for A. marina (52 species) than for R. mucronata (44 species), whereas 40 species commonly existed in both mangrove covers. A higher density of nematodes was found in sediments of sandy nature, whereas there was lower total organic carbon compared to silt/clay composition; epigrowth feeders were dominant over the other feeding groups based on organic enrichment in surface sediments. Principal component analysis clearly explained the relationship between the environmental parameters of various months. Higher R values of analysis of similarities revealed significant differences in nematode assemblages between months, and it was quite evident by non-metric multidimensional scaling. Diversity indices showed higher values in the dry months. RELATE analysis explained serial changes in nematode species composition between months, and a relationship between biotic and abiotic variables was clarified using the BIO-ENV procedure. Viscosia spp., Metachromadora spp., Theristus spp., and Sphaerolaimus spp. were candidate species of A. marina leaf interaction by observation.

Diversity of macrofauna from continental shelf off Singarayakonda (southeast coast of India).

The present study was undertaken to study the benthic productivity of shelf region off Krishna River mouth. Standing stock of macrobenthos and its distribution were studied. Sampling was done onboard FORV Sagar Sampada from depths as 30, 50, 75, 100, 150 and 200 m using Smith-McIntyre grab having a bite area of 0.2 m2. After identification, data were treated using statistical package PRIMER v6. The nature of the sediment was medium sand up to 150 m depth and fine silt at 200 m. The benthic biomass (0.2977-3.1091 mg 0.2 m(-2)), abundance (58-289 nos. 0.2 m(-2) and number of species (12-48) decreased with increase in depth. The total number of species recorded was 69. Species estimators showed the possibility of collecting 129 species (Chao1) with intense sampling. Polychaetes formed the largest group with 40 species followed by molluscs (15 species) and crustaceans (14 species). The Spearman rank correlation (Rho) value (0.513) which was significant at 1.1% showed gradual change in species composition with increase in depth. The Pi value (3.78) comparing the similarity of benthos at 200 m depth with those of other depths (30, 150, 100, 75 and 50 m) showed significant differences (0.6%). Matching of biotic variables with that of environment showed the influence of dissolved oxygen on the distribution of macrobenthos (Rho 0.757). Intense sampling should be done to record all the species as shown by species estimators besides studying shelf productivity off other rivers and relating it with nutrient discharge and other environmental factors including sediment nature.