Digestive chitinolytic activity in marine fishes of Monterey Bay, California

Chitinolytic activities, both chitinase (EC 3.2.1.14) and minimum chitobiase (beta-N-acetyl-D-glucosaminidase; EC 3.2.1.30), were measured in stomach and intestinal tissues and their contents, from 13 fish species. Higher activities were found in the tissues than in the gut contents, and higher activities were seen in the stomachs than in the intestines. Demersal species exhibited chitobiase activities very close to their chitinase activities, suggesting that these fishes can degrade chitin completely to its soluble, absorbable monomer, N-acetyl-glucosamine. This suggests that these species may catabolize chitin not just to penetrate prey exoskeletons but also to derive nutrients from the chitin itself. In contrast, three mesopelagic species exhibited low chitobiase but high chitinase activities. This chitobiase limitation correlated strongly with gastrointestinal tract morphology, with the myctophids having the greatest chitobiase limitation and the shortest alimentary tracts. The high chitinase activities measured in the myctophids reflect their ability to rapidly disrupt prey exoskeletons ingested during their nightly feeding in surface waters. Their chitobiase activities are greatly reduced because with rapid meal evacuation through a short gut there is little time for processing and limited energetic advantage in the complete degradation of chitin. These results suggest multiple roles for chitinolytic enzymes in marine fishes and that feeding habits and frequency may have a bearing on the evolution of their digestive enzymes systems.     

Biogeography of the marine birds of a confined sea, the Mediterranean

Aim The Mediterranean sea is a winter productive oligotrophic basin where Atlantic water replaces water lost through evaporation, this influx being a major source of productivity and fertility. The long coastlines and the large number of islands cause high oceanographic heterogeneity. Moreover, during its geological history, it has dried out several times. So we describe the consequences of these particular features on species richness, distribution, and breeding ecology of marine birds. Location The Mediterranean sea (including the Black Sea and the Sea of Azov) communicates with the Atlantic Ocean only through a 14 km wide channel (Straits of Gibraltar), and since 1869, with the Red Sea through the Suez Canal. Methods The Mediterranean was subdivided into different areas, according to physical oceanographic entities and productivity, linked to numbers and distribution of both breeding and wintering marine birds (defined as species strongly dependent on marine resources, breeding only on islands and/or the coastline). Results The total marine bird biomass, and species diversity, are lower in the Mediterranean than in the near Atlantic. The eastern Mediterranean, with lowest primary productivity, contains fewer marine bird taxa than the more productive western part. Taxa which mainly occur in the western and southern parts of the Mediterranean migrate through the Straits of Gibraltar to winter in the southern Atlantic, while those inhabiting the northern and eastern parts are sedentary, as a result of differences in species composition. Northern coastal basin communities (i.e. the Tyrrhenian and the Balearic Seas), are composed of less pelagic, and earlier breeding species, that rear chicks during the productive season. These latter taxa are actually the most typical Mediterranean taxa, in terms of endemism. Main conclusions The Mediterranean marine bird community is not tropical, but rather, shows the highest affinity with the Atlantic temperate community. Its level of endemism is however high and comparable to other confined basins such as the Red Sea.     

Synoptic water clarity assessment in the Florida Keys using diffuse attenuation coefficient estimated from Landsat imagery

The diffuse attenuation coefficient, K (m^{− 1}), is a measure of the effective attenuation of light in the water column. It characterizes water clarity and is used as a proxy for water quality. Mapping of shallow water benthic habitats using optical means, including daytime visible satellite imagery, requires knowledge of K to correct for water column effects such as light absorption and scattering. Traditionally, K is derived from imagery using a priori knowledge of bottom types at different depths and specific locations, and assuming that light attenuates exponentially with depth. This technique is applied to three Landsat 7 satellite images (February, May, and July 2000) from the Florida Keys Reef Tract between Key Largo and Key West. Interpolated depth data, initially from NOAA vector chart data, with uncertainties of ±0.5 m, were draped over 30 m spatial resolution Landsat satellite imagery. K was derived for 27 sites where bright sand could be observed at depths between 3 and 20 m. The blue and green bands (Landsat bands 1 and 2 at 450–520 nm and 520–600 nm, respectively) provided K values consistent with time and location. Average K values for bands 1 and 2, respectively, were 0.029 and 0.043 m^{− 1} (Lower Keys), 0.050 and 0.072 m^{− 1} (Middle Keys), and 0.063 and 0.082 m^{− 1} (Upper Keys). The red band (band 3, 630–690 nm) provided more ambiguous and erroneous results with several negative K values, attributed primarily to three factors use of a simple atmospheric correction, the high absorption and rapid attenuation of red light in water, and low radiometric sensitivity of the Landsat ETM + sensor. Despite the fact that these observations were a snapshot in time, trends were observed for the Upper, Middle, and Lower Keys, possibly due to the influence of more turbid Florida Bay waters.     

Potential impacts of wave‐powered marine renewable energy installations on marine birds

One potential approach to combat the impacts of climate change is the expansion of renewable energy installations, leading to an increase in the number of wave‐powered marine renewable energy installations (MREIs). The consequences of increased use of these devices for birds are unknown. Here we describe the wave‐powered energy‐generating devices currently either operational or in development and review the potential threats and benefits of these to marine birds, their habitats and prey. Direct negative effects include risk of collision, disturbance, displacement and redirection during construction, operation and decommissioning. Above‐water collision is a particular concern with wind‐powered devices, but, because of their low profiles, the collision risk associated with wave‐powered devices is likely to be much lower. Conversely, wave devices also pose the novel threat of underwater collision. Wave‐energy‐generating devices may indirectly impact marine birds by altering oceanographic processes and food availability, with implications for trophic cascades. Through appropriate mitigation, wave‐powered MREIs offer the potential to enhance habitats. Direct positive effects may include provision of roosting sites, and indirect positive effects may include prey aggregation due to suitable substrates for sessile organisms or because they act as de facto protected areas. The cumulative effect of these could be the improvement and protection of foraging opportunities for marine birds. Recent studies have been critical of the methods used in the assessment of wind‐powered MREI impacts, which lack sufficient sample sizes, controls or pre‐development comparisons. Here we suggest solutions for the design of future studies into the effects of MREIs. Wave‐powered MREIs are certain to become part of the marine environment, but with appropriate planning, mitigation and monitoring they have the potential to offer benefits to marine birds in the future.     

基于遥感技术的鄱阳湖采砂对水体透明度的影响

采砂是一项具有巨大生态影响的经济活动。其引起沉积泥沙的再悬浮,降低水体透明度,减弱水下光环境以及产生一系列的生态影响。旨在利用遥感技术监测鄱阳湖自2001年开始的采砂活动对水体透明度的影响。时间序列的IANDSAT影像用于船只的识别和同期的水体透明度反演,MODIS影像用于估计湖区2000—2005年6—10月期间水体透明度的动态变化。结果显示鄱阳湖北部自2001年以来随着船只数目的增加水体透明度显著下降。结合对船只最终目的地以及船只分布与水体透明度变化一致性等方面的分析,可以确认采砂是引起此区域水体透明度下降的主要原因。夏季频繁发生的长江江水倒灌推动鄱阳湖北部的浑浊水体向南移动,从而扩大采砂的影响范围至鄱阳湖中部,甚至南部。采砂繁荣了地方经济,同时也对鄱阳湖生态系统具有重大的负面影响。平衡经济发展与生态保护之间的关系,将因采砂而造成的负面影响下降到最低限度,使鄱阳湖的各种生态功能全面发挥是当务之急。     

栖息地演变与人为干扰对升金湖越冬水鸟的影响

2002年10月—2003年4月,选择安徽升金湖6个不同干扰程度和栖息地质量的固定监测点,研究人为干扰对升金湖越冬水鸟分布格局的影响;同时结合前期调查数据,研究栖息地演变对升金湖越冬水鸟的影响.结果表明:同一越冬期不同监测点水鸟种类和数量与栖息地质量无显著相关关系,但水鸟数量与栖息地干扰程度显著负相关;不同年份升金湖越冬水鸟种类和数量与栖息地质量显著相关.升金湖越冬水鸟存在的主要威胁包括栖息地丧失、人为活动干扰以及生物杀灭剂的影响.提出了一些保护升金湖越冬水鸟的建议.     

Strong effects of occasional drying on subsequent water clarity and cyanobacterial blooms in cool tropical reservoirs

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Effects of water clarity and other environmental factors on trophic niches of two sympatric piscivores

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Pattern in the distribution of Britain's upland breeding birds

We use a quantitative approach to identify fifty-eight species of birds which breed in association with the British uplands. Similarities and differences between this list of 'upland birds' and previous more subjective lists are discussed. We then study pattern in the distribution of these species throughout the uplands. A high degree of regionalization is found, and interpreted in terms of the habitat composition of different regions, and known bird–habitat associations. Different regions differ widely, not only with respect to their bird species composition, but also in the number and conservation importance of their upland bird assemblages. In particular, we contrast the uplands of Wales and England with those of Scotland. The Welsh and English uplands contain a relatively low number of upland bird assemblages and are divided into a few large regions, each dominated by a single assemblage type. In comparison, the Scottish uplands are more varied, both in terms of the total number of assemblages, and the range of assemblages found at a small scale. The study provides a means of viewing any upland region within the national context.     

Habitat modelling of tracking data from multiple marine predators identifies important areas in the Southern Indian Ocean

Aim

The distribution of marine predators is driven by the distribution and abundance of their prey; areas preferred by multiple marine predator species should therefore indicate areas of ecological significance. The Southern Ocean supports large populations of seabirds and marine mammals and is undergoing rapid environmental change. The management and conservation of these predators and their environment relies on understanding their distribution and its link with the biophysical environment, as the latter determines the distribution and abundance of prey. We addressed this issue using tracking data from 14 species of marine predators to identify important habitat.

Location

Indian Ocean sector of the Southern Ocean.

Methods

We used tracking data from 538 tag deployments made over a decade at the Subantarctic Prince Edward Islands. For each real track, we simulated a set of pseudo‐tracks that allowed a presence‐availability habitat modelling approach that estimates an animal's habitat preference. Using model ensembles of boosted regression trees and random forests, we modelled these tracks as a response to a set of 17 environmental variables. We combined the resulting species‐specific models to evaluate areas of mean importance.

Results

Real tracking locations covered 39.75 million km², up to 7,813 km from the Prince Edward Islands. Areas of high mean importance were located broadly from the Subtropical Zone to the Polar Frontal Zone in summer and from the Subantarctic to Antarctic Zones in winter. Areas of high mean importance were best predicted by factors including wind speed, sea surface temperature, depth and current speed.

Main conclusions

The models and predictions developed here identify important habitat of marine predators around the Prince Edward Islands and can support the large‐scale conservation and management of Subantarctic ecosystems and the marine predators they sustain. The results also form the basis of future efforts to predict the consequences of environmental change.

     

Unexpected presence of the nitrogen-fixing symbiotic cyanobacterium UCYN-A in Monterey Bay,California

In the last decade, the known biogeography of nitrogen fixation in the ocean has been expanded to colder and nitrogen-rich coastal environments. The symbiotic nitrogen-fixing cyanobacteria group A (UCYN-A) has been revealed as one of the most abundant and widespread nitrogen-fixers, and includes several sublineages that live associated with genetically distinct but closely related prymnesiophyte hosts. The UCYN-A1 sublineage is associated with an open ocean picoplanktonic prymnesiophyte, whereas UCYN-A2 is associated with the coastal nanoplanktonic coccolithophore Braarudosphaera bigelowii, suggesting that different sublineages may be adapted to different environments. Here, we study the diversity of nifH genes present at the Santa Cruz Municipal Wharf in the Monterey Bay (MB), California, and report for the first time the presence of multiple UCYN-A sublineages, unexpectedly dominated by the UCYN-A2 sublineage. Sequence and quantitative PCR data over an 8-year time-series (2011–2018) showed a shift toward increasing UCYN-A2 abundances after 2013, and a marked seasonality for this sublineage which was present during summer-fall months, coinciding with the upwelling-relaxation period in the MB. Increased abundances corresponded to positive temperature anomalies in MB, and we discuss the possibility of a benthic life stage of the associated coccolithophore host to explain the seasonal pattern. The dominance of UCYN-A2 in coastal waters of the MB underscores the need to further explore the habitat preference of the different sublineages in order to provide additional support for the hypothesis that UCYN-A1 and UCYN-A2 sublineages are different ecotypes.     

Near real-time, autonomous detection of marine bacterioplankton on a coastal mooring in Monterey Bay, California, using rRNA-targeted DNA probes

A sandwich hybridization assay (SHA) was developed to detect 16S rRNAs indicative of phylogenetically distinct groups of marine bacterioplankton in a 96-well plate format as well as low-density arrays printed on a membrane support. The arrays were used in a field-deployable instrument, the Environmental Sample Processor (ESP). The SHA employs a chaotropic buffer for both cell homogenization and hybridization, thus target sequences are captured directly from crude homogenates. Capture probes for seven of nine different bacterioplankton clades examined reacted specifically when challenged with target and non-target 16S rRNAs derived from in vitro transcribed 16S rRNA genes cloned from natural samples. Detection limits were between 0.10–1.98 and 4.43– 12.54 fmole ml⁻¹ homogenate for the 96-well plate and array SHA respectively. Arrays printed with five of the bacterioplankton-specific capture probes were deployed on the ESP in Monterey Bay, CA, twice in 2006 for a total of 25 days and also utilized in a laboratory time series study. Groups detected included marine alphaproteobacteria, SAR11, marine cyanobacteria, marine group I crenarchaea, and marine group II euryarchaea. To our knowledge this represents the first report of remote in situ DNA probe-based detection of marine bacterioplankton.     

Distribution and biology of marine cladocerans in the coastal waters of southern China

Geographical and seasonal distributions of marine cladocerans in the coastal waters of southern China were studied. Penilia avirostris was the most common species, followed by Evadne tergestina and Podon schmackeri. P. avirostris and E. tergestina were most common during summer. P. schmackeri, found only in a small bay northeast of Hong Kong, showed no clear seasonal pattern of occurrence. P. avirostris and E. tergestina were found at temperatures ranging from 16–32°C and salinity ranging from 7.3–37.2. P. schmackeri was restricted to a temperature range of 17–29°C and a salinity range of 31.0–37.2. No significant relationships between marine cladoceran abundance and chlorophyll a concentration were found in samples taken from Tolo Harbour. Parthenogenetic brood size of P. avirostris and E. tergestina ranged from 1 to 14, while P. schmackeri was found to carry up to 19 embryos per brood. No geographical trend in fecundity patterns was observed. No correlation was found between body length and brood size. The occurrence of females with resting eggs was rare.     

大连地区海生物中致病性弧菌及气单胞菌分布的研究

本文首次报道了大连地区海产品中致病性弧菌及气单胞菌生态分布的研究结果。从152份海产品中共检出88株致病性弧菌及气单胞菌,检出率为57.9％.在检查欧氏六线鱼、太平洋鲱鱼、蓝色马鲛;蝼蛄虾;紫贻贝、杂色蛤仔和毛蚶共7种海产品中,检出9种致病性弧菌和1种气单胞菌,即溶藻弧菌、副溶血性弧菌、麦氏弧菌、少女鱼弧菌、弗尼斯弧菌、拟态弧菌、河弧菌、非01群霍乱弧菌和创伤弧菌。鱼虾类中菌株的检出率明显高于贝类。检出菌株中溶藻弧菌所占比例最高(54.5％),其次为副溶血性弧菌(27.3％)。首次从海生物中分离出嗜水气单胞菌、少女鱼弧菌等致病原因菌株.     

Land use changes affect distributional patterns of desert birds in the Baja California peninsula, Mexico

Reliable plans for desert bird conservation will depend on accurate prediction of habitat change effects on their distribution and abundance patterns. Predictive models can help highlight relationships between human‐related and other environmental variables and the presence of desert bird species. Presence/absence of 30 desert bird species of Baja California peninsula was modelled on the basis of explanatory variables taken from the field, maps, and digital imagery. Generalized linear models were fit to each bird species using both variables representing human activity and other environmental factors as predictors that might influence distribution. Probability of species presence was used as a habitat suitability index to evaluate the effect of human activity when the model contained a significant human activity variable. No differences were found in bird species richness between natural sites and those transformed by agriculture or urbanization. Of 59 bird species recorded in surveys, 34% were positively or negatively associated with human‐transformed habitats. Fourteen species seem to benefit from transformation of natural vegetation by agriculture or urbanization, while six were negatively affected. Sensitivity analyses of final models indicated all were robust. Results suggest that the occurrence of a large percentage of bird species inhabiting scrub habitats is sensitive to human habitat transformation. This finding has important conservation implications at regional scale as fragmentation and conversion of desert ecosystems into agricultural and urban areas affect the distribution of species that are highly selective for scrub habitat. Land use and anthropogenic activities seem to change ecological patterns at large spatial scales, but other factors could drive species richness distribution too (i.e. individual species response, species–energy relationships). The spatial modelling approach at regional scale used in this study can be useful for designing natural resource management plans in the Sonoran desert scrub.     

The marine flora of the Cap Blanc peninsula: its distribution and affinities

The shores of the Cap Blanc peninsula, along which runs the border between Mauritania and Western Sahara (former Spanish Sahara), were studied in November 1975. Littoral zonation is described and an annotated list is presented of the 188 species of algae now known from Mauritania and Western Sahara together with a further 23 species identified only to genus. In this present study 88 species of algae (excluding Cyanophyceae) were determined resulting in an increase of 67% and 37% respectively for the previously known marine floras of Western Sahara and Mauritania. Of 97 marine algae known from specific localities on the Cap Blanc peninsula, only 21 are common to both its eastern and western sides. Several tropical species reach their northern limit on the eastern side of the peninsula and many warm-temperate species reach their southernmost limit on the western side. Thus the Cap Blanc peninsula appears to represent a boundary between the warm temperate seaweed flora of North West Africa and the subtropical transition flora of Mauritania and Sénégal to the south.     

Epidemiology and potential land-sea transfer of enteric bacteria from terrestrial to marine species in the Monterey Bay Region of California

Marine mammals are at risk for infection by fecal-associated zoonotic pathogens when they swim and feed in polluted nearshore marine waters. Because of their tendency to consume 25-30% of their body weight per day in coastal filter-feeding invertebrates, southern sea otters (Enhydra lutris nereis) can act as sentinels of marine ecosystem health in California. Feces from domestic and wildlife species were tested to determine prevalence, potential virulence, and diversity of selected opportunistic enteric bacterial pathogens in the Monterey Bay region. We hypothesized that if sea otters are sentinels of coastal health, and fecal pollution flows from land to sea, then sea otters and terrestrial animals might share the same enteric bacterial species and strains. Twenty-eight percent of fecal samples tested during 2007-2010 were positive for one or more potential pathogens. Campylobacter spp. were isolated most frequently, with an overall prevalence of 11%, followed by Vibrio cholerae (9%), Salmonella spp. (6%), V. parahaemolyticus (5%), and V. alginolyticus (3%). Sea otters were found positive for all target bacteria, exhibiting similar prevalences for Campylobacter and Salmonella spp. but greater prevalences for Vibrio spp. when compared to terrestrial animals. Fifteen Salmonella serotypes were detected, 11 of which were isolated from opossums. This is the first report of sea otter infection by S. enterica Heidelberg, a serotype also associated with human clinical disease. Similar strains of S. enterica Typhimurium were identified in otters, opossums, and gulls, suggesting the possibility of land-sea transfer of enteric bacterial pathogens from terrestrial sources to sea otters.     

Enumeration and speciation of enterococci found in marine and intertidal sediments and coastal water in southern California

AIMS: To determine the levels and species distribution of enterococci in intertidal and marine sediments and coastal waters at two beaches frequently in violation of bacterial water standards. METHODS AND RESULTS: Faecal indicator bacteria were extracted from sediment and enumerated using membrane filtration. High levels of enterococci were detected in intertidal sediments in a seasonal river and near a storm drain outlet. Low levels were found in marine sediments at 10 m depths and in surf zone sand. Bacterial isolates presumptively identified as Enterococcus on mEI media were speciated. The predominant species found in both water and sediment included Enterococcus faecalis, Enterococcus faecium, Enterococcus hirae, Enterococcus casseliflavus and Enterococcus mundtii. A number of isolates (11-26%) from regulatory water samples presumptively identified as enterococci on mEI media were subsequently identified as species other than Enterococcus. At both study sites, the distribution of species present in water was comparable with those in sediments and the distribution of species was similar in water samples passing and exceeding bacterial indicator standards. CONCLUSIONS: High levels of Enterococcus in intertidal sediments indicate retention and possible regrowth in this environment. SIGNIFICANCE AND IMPACT OF THE STUDY: Resuspension of enterococci that are persistent in sediments may cause beach water quality failures and calls into question the specificity of this indicator for determining recent faecal contamination.