Sea turtle nesting distributions and oceanographic constraints on hatchling migration

Patterns of abundance across a species''s reproductive range are influenced by ecological and environmental factors that affect the survival of offspring. For marine animals whose offspring must migrate long distances, natural selection may favour reproduction in areas near ocean currents that facilitate migratory movements. Similarly, selection may act against the use of potential reproductive areas from which offspring have difficulty emigrating. As a first step towards investigating this conceptual framework, we analysed loggerhead sea turtle (Caretta caretta) nest abundance along the southeastern US coast as a function of distance to the Gulf Stream System (GSS), the ocean current to which hatchlings in this region migrate. Results indicate that nest density increases as distance to the GSS decreases. Distance to the GSS can account for at least 90 per cent of spatial variation in regional nest density. Even at smaller spatial scales, where local beach conditions presumably exert strong effects, at least 38 per cent of the variance is explained by distance from the GSS. These findings suggest that proximity to favourable ocean currents strongly influences sea turtle nesting distributions. Similar factors may influence patterns of abundance across the reproductive ranges of diverse marine animals, such as penguins, eels, salmon and seals.     

北部湾中部海域底质沉积物中的有孔虫

本文对北部湾中部海域水深2.4m到61m、共计184个站位表层沉积物中的有孔虫进行研究。结果显示浮游有孔虫丰度非常低,种类也较稀少,仅在南侧水深较大的少数站位有发现,且含量不超过5%;而底栖有孔虫则较丰富,多数样品中以含有螺旋式与平旋式的玻璃质壳类型为主,暖水或大型底栖有孔虫分子常见。和其它海区相较而言,该海域底栖有孔虫中胶结壳类含量偏高,可能与沉积物底质颗粒较粗及海水盐度较低有关。该研究详细报道了底栖有孔虫主要属种在北部湾的分布特征。与海洋环境对比显示,水深和沉积物底质类型是影响这些属种平面分布的主要因素,而湾外温暖水团则是控制暖水种分子分布的另一重要因素。     

FIRST HARMFUL DINOPHYSIS (DINOPHYCEAE,DINOPHYSIALES) BLOOM IN THE U.S. IS REVEALED BY AUTOMATED IMAGING FLOW CYTOMETRY1

Imaging FlowCytobot (IFCB) combines video and flow cytometric technology to capture images of nano‐ and microplankton (～10 to >100 μm) and to measure the chlorophyll fluorescence associated with each image. The images are of sufficient resolution to identify many organisms to genus or even species level. IFCB has provided >200 million images since its installation at the entrance to the Mission‐Aransas estuary (Port Aransas, TX, USA) in September 2007. In early February 2008, Dinophysis cells (1–5 · mL^?1) were detected by manual inspection of images; by late February, abundance estimates exceeded 200 cells · mL^?1. Manual microscopy of water samples from the site confirmed that D. cf. ovum F. Schütt was the dominant species, with cell concentrations similar to those calculated from IFCB data, and toxin analyses showed that okadaic acid was present, which led to closing of shellfish harvesting. Analysis of the time series using automated image classification (extraction of image features and supervised machine learning algorithms) revealed a dynamic phytoplankton community composition. Before the Dinophysis bloom, Myrionecta rubra (a prey item of Dinophysis) was observed, and another potentially toxic dinoflagellate, Prorocentrum, was observed after the bloom. Dinophysis cell‐division rates, as estimated from the frequency of dividing cells, were the highest at the beginning of the bloom. Considered on a daily basis, cell concentration increased roughly exponentially up to the bloom peak, but closer inspection revealed that the increases generally occurred when the direction of water flow was into the estuary, suggesting the source of the bloom was offshore.     

Spatial and bathymetric trends in Harpacticoida (Copepoda) community structure in the Northern Gulf of Mexico deep-sea

Harpacticoid copepod community structure was analyzed at 43 stations in the northern Gulf of Mexico deep-sea to test regional and bathymetric patterns of diversity in relation to environmental variables and topographic complexity of the continental slope. Depth, longitude, and proximity to the Florida Escarpment significantly affect average phylogenetic diversity, but basins and canyons do not. Multivariate analysis reveals a significant inverse relationship between diversity and POM flux, which is confirmed by significant region-scale depth and longitude differences. Although species richness declines linearly with increasing depth, the expected number of species (rarefraction) is maximized at approximately 1200 m, and average taxonomic and phylogenetic diversity continue to increase with depth, suggesting greater morphological or functional harpacticoid diversity with increasing depth. Most stations have unique species compositions, suggesting high regional (2200 species) and global (10⁵-10⁶ species) diversity by extrapolation. Therefore, processes maintaining harpacticoid diversity in the northern Gulf of Mexico deep-sea seem to rely on both small-scale dispersal and large-scale food supply mechanisms.     

Sinking rates of late-stage fish larvae: Implications for larval ingress into estuarine nursery habitats

Many species spawn in oceanic waters yet their juvenile stages use nearshore and estuarine habits and the bio-physical mechanisms by which late-larvae enter these juvenile habitats may be an important bottleneck in the population dynamics of these species. To provide parameters for the development of larval ingress models, sinking rates were measured of the late-stage larvae of six fish species: Atlantic croaker (Micropogonias undulatus), spot (Leiostomus xanthurus), Atlantic menhaden (Brevoortia tyrannus), summer flounder (Paralichthys dentatus), southern flounder (P. lethostigma), and gulf flounder (P. albigutta). Species-specific differences were found in sinking rates; Atlantic croaker had the slowest sinking rates and Atlantic menhaden and the three flounder species had the fastest sinking rates. Additionally, sinking rates increased for all species as length increased. The total amount of variability explained in sinking rates was low (20–50%), indicating a large amount of variability at the level of the individual. The observed patterns in sinking rates were then combined with previous studies on the mechanisms of larval ingress to present species-specific conceptual models of ingress.     

Egg production and early development of Thysanoessa inermis and Euphausia pacifica (Crustacea: Euphausiacea) in the northern Gulf of Alaska

Early life history patterns were studied in the dominant euphausiids from the northern Gulf of Alaska (GOA) in 2001-2004. Gravid females of Thysanoessa inermis were observed in April and May. Brood size varied from 10 to 1021 eggs with an average of 138 ± 19 (95% CI) eggs female^− 1. Most gravid females started to release eggs within the first 2 days of incubation. The average number of eggs released per female was similar in incubation Day 1 and 2, but significantly smaller on Day 3 and 4. About 25% of the females were continuously releasing eggs over 3 days rather than producing a single distinctive brood. In contrast, gravid females of Euphausia pacifica were observed from early July through October. Most gravid females released eggs on the first day of observation, while only 2% of females produced eggs repeatedly. Brood size varied from 20 to 246 eggs with an average of 102 ± 12 (95% CI) eggs female^− 1. The relationship between E. pacifica brood size and ambient chlorophyll-a concentration was sigmoidal (r² = 0.73), with food saturated brood size of 144 ± 14(SE, P < 0.001) eggs, and half-saturation occurring at 0.46 ± 0.02(SE, P < 0.001) mg chlorophyll-a m^− 3. The average interbrood interval of E. pacifica reared at 12 °C and satiated food conditions in the laboratory was ∼ 8 days, suggesting their potential individual fecundity in the GOA was 1148-1530 eggs per spawning season. Hatching and early development (from egg to furcilia stage) was studied under 5 °C, 8 °C and 12 °C. Hatching was nearly synchronous and lasted 3-6 h, depending on incubation temperature. Development times from egg to the first furcilia stage ranged between 20 and 33 days for T. inermis, and 15 and 45 days for E. pacifica at 12 °C and 5 °C, respectively.     

Coastal eutrophication assessment in the United States

Recent national assessments document that nitrogen-driven coastal eutrophication is widespread and increasing in the United States. This significant coastal pollution problem includes impacts including increased areas and severity of hypoxic and anoxic waters; alteration of food webs; degradation and loss of sea grass beds, kelp beds and coral reefs; loss of biodiversity; and increased incidences and duration of harmful algal blooms. In this paper, we review two complementary approaches to assessing the causes and consequences of these trends, as well as potential remedies for them. The first is a national-scale assessment, drawn primarily from expert knowledge of those most familiar with the individual estuaries and integrated into a common analysis framework. The second approach, focused on the Mississippi/Atchafalaya basin – the largest US drainage basin – draws upon both quantitative and qualitative analyses within a comprehensive framework, Integrated Assessment.     

蓝尾石龙子杭州和宁德种群繁殖生活史特征的差异

测定处于不同纬度的浙江杭州和福建宁德的蓝尾石龙子(Eumeceselegans)种群的个体大小和繁殖特征。宁德种群的产卵时间为5月27日—6月22日,早于高纬度杭州种群(6月4日—7月12日)。宁德种群最小繁殖雌体及性成熟个体大小均显著小于杭州种群。宁德和杭州两种群的相对窝卵重无显著差异;当统计去除母体体长的影响之后,两地种群的窝卵数和窝卵重也无显著差异,但杭州种群的卵重量显著大于宁德种群。蓝尾石龙子窝卵数和卵重量呈负相关,窝卵数和卵大小的权衡存在种群间差异。特定窝卵数条件下,杭州种群的卵重量显著大于宁德种群。由此可见,蓝尾石龙子种群间的繁殖生活史特征存在显著差异,而且与母体大小的差异密切相关。推测不同纬度地区的蓝尾石龙子种群的繁殖策略存在差异。     

A suite of citrate-derived siderophores from a marine Vibrio species isolated following the Deepwater Horizon oil spill

Nearly all microbes require iron for growth. The low concentration of iron found in the ocean makes iron acquisition a particularly difficult task. In response to these low iron conditions, many bacteria produce low-molecular-weight iron-binding molecules called siderophores to aid in iron uptake. We report herein the isolation and structural characterization of a suite of amphiphilic siderophores called the ochrobactins-OH, which are produced by a Vibrio species isolated from the Gulf of Mexico after the 2010 Deepwater Horizon oil spill. The citrate-based ochrobactins-OH are derivatives of aerobactin, replacing the acetyl groups with fatty acid appendages ranging in size from C8 to C12, and are distinctly different from the ochrobactins in that the fatty acid appendages are hydroxylated rather than unsaturated. The discovery of the marine amphiphilic ochrobactin-OH suite of siderophores increases the geographic and phylogenetic diversity of siderophore-producing bacteria.