Accelerating Trophic-level Dysfunction in Kelp Forest Ecosystems of the Western North Atlantic

We use archaeological, historical, ecological, and fisheries data to identify three distinct and sequential phases in the trophic structure of kelp forests in the western North Atlantics Gulf of Maine. Phase 1 is characterized by vertebrate apex predators such as Atlantic cod, haddock, and wolffish and persisted for more than 4,000 years. Phase 2 is characterized by herbivorous sea urchins and lasted from the 1970s to the 1990s. Phase 3 is dominated by invertebrate predators such as large crabs and has developed since 1995. Each phase change resulted directly or indirectly from fisheries-induced trophic-level dysfunction, in which populations of functionally important species at higher trophic levels fell below the densities necessary to limit prey populations at lower trophic levels. By using fractional trophic-level analysis, we found that phase changes occurred rapidly (over a few years to a few decades) as well as relatively recently (over the past half-century). Interphase durations have declined as fishing effects have accelerated in recent years. The naturally low species diversity of the kelp forest ecosystem we studied may facilitate rapid changes because the redundancy within each trophic level is low. If the biodiversity within controlling trophic levels is a buffer against trophic-level dysfunction, then our observations from Maine may be predictive of the fate of other, more diverse systems. If fishing successively targets most, or all, strong interactors at higher trophic levels, then as those population densities decline, the potential for trophic-level dysfunction and associated instabilities will increase.     

环渤海湾苹果产区老果园与连作果园土壤线虫群落特征

应用类群多样性、类群丰富度、个体密度和功能类群指数等群落参数,于2009年5-10月分3次对环渤海湾苹果栽植区老果园不同位置和连作果园取样研究了土壤线虫群落特征。结果表明:苹果连作对果园土壤生物环境具有明显的恶化作用,连作果园土壤环境条件恶劣;对功能类群指数的统计表明,苹果连作明显改变了果园土壤中植物寄生性线虫r-选择和k-选择的比例,与自由生活线虫比较,连作对植物寄生线虫影响更明显;连作提高了果园的土壤线虫PPI/MI,说明连作对果园土壤健康的扰动最大;土壤不同食性线虫数量统计结果显示,环渤海湾苹果栽植区植食性线虫数量未达线虫伤害阈值,线虫不是引起环渤海湾地区苹果连作障碍的主要原因。     

海州湾人工鱼礁二期工程海域大型底栖生物初步研究

2005、2007、2008年每年2月、5月和8月按《海洋监测规范》中大型底栖动物调查方法,分别对海州湾人工鱼礁二期工程施工海域(34°52′~30°55′N、119°25′34″~119°26′34″E)采用阿氏拖网进行了调查。监测结果显示,底栖动物的种类数较投放前有所增加;底栖动物年均总生物量逐年降低,2005年(1.0016g/m2)>2007年(0.9681g/m2)>2008年(0.7327g/m2);底栖生物群落生物多样性指数(H′)和丰富度(d)年均值呈逐年上升趋势,并且具有明显的季节性变化,春季最高,夏季次之,秋季最低;投礁前夏季的底栖动物的群落处于稳定状态而投礁后处于中度扰动状态。监测结果表明,鱼礁工程建设已经对投礁海域的底栖动物种类数、总生物量、多样性指数以及群落稳定性产生了一定程度的影响。     

Purification and properties of hepatic glutamine synthetases from the ureotelic gulf toadfish, Opsanus beta

The cytoplasmic and mitochondrial forms of glutamine synthetase (GSase) were purified from the liver of the gulf toadfish Opsanus beta by modifications of methods previously applied to dogfish shark to examine their kinetic and structural properties. Both isozymes have subunit molecular weights of approximately 42 kDa (by SDS-PAGE) and native molecular weights of approximately 365 kDa (by gel filtration chromatography), suggesting an octomeric arrangement of the native enzymes. Identity of the purified proteins as GSase was further confirmed by western blot analysis using rabbit anti-chicken GSase antibodies. The requirement for MgCl₂ and several kinetic properties (e.g.,K_ms for glutamate, ATP and ammonia) of the two isozymes were very similar. Also notable was that both isozymes had K_ms for ammonia in the micromolar range (like the dogfish enzyme). These results suggest that the enzymes are probably easily saturated with ammonia under physiological conditions. The two GSase isozymes differed substantially in terms of inhibition by methionine sulfoximine, pH optima, specific activity and ratios of transferase to biosynthetic activities. Given the similarities in size, these results suggest that the molecular model of a single gene coding for both isozymes as has been demonstrated in the dogfish shark may not apply to the toadfish GSases.     

The phytoplankton of the internal Gulf of Olbia (North-East Sardinia) between July 1992 and July 1993

Abstract

The density variations and phytoplankton structure of the internal Gulf of Olbia (north-east Sardinia) from July 1992 to July 1993 are described.

The most important class was the Bacillariophyceae, because it accounted for the maximum values and because it dominated over about one-third of the study cycle. The picoplankton was present practically all the year round with the greatest development from September to March. Prymnesiophyceae, Dinophyceae, Cyanophyceae and Euglenophyceae were found more numerously in summer and autumn 1992 than in the rest of the year, while Bacillariophyceae, Chlorophyceae and Chrysophyceae were mostly found in spring and summer 1993.

Among the 16 species that expressed the highest mean yearly density values (greater than 1×10⁴ cell I^-1), 10 were Bacillariophyceae, 2 Dinophyceae, 3 Chrysophyceae and 1 Chlorophycea. The Bacillariophyceae have also been the dominant class in floristic terms (49 taxa on 95 total), followed by the Dinophyceae (26), the Chlorophyceae (5), the Chrysophyceae (5), the Prymnesiophyceae (4), the Prasinophyceae (2), the Euglenophyceae (2) and the Cyanophyceae (2).     

Presence of the telescope fish Mendosoma lineatum in Patagonian waters,a new species in the ichthyological fauna from the south‐west Atlantic Ocean

The presence of the telescope fish Mendosoma lineatum in Patagonian waters of Argentina is reported. Mendosoma lineatum is the second species of the Latridae recorded in the south‐west Atlantic Ocean and its presence in Patagonia is an addition to both the ichthyological fauna of the Argentinean Sea and the south‐west Atlantic Ocean.     

Vertical zonation and functional diversity of fish assemblages revealed by ROV videos at oil platforms in The Gulf

An assessment of vertical distribution, diel migration, taxonomic and functional diversity of fishes was carried out at offshore platforms in The (Arabian–Iranian–Persian) Gulf. Video footage was recorded at the Al Shaheen oil field between 2007 and 2014 using a remotely operated vehicle (ROV). A total of 12 822 individual fishes, from 83 taxonomic groups were recorded around the platforms. All the species identified are considered native to The Gulf, although Cyclichthys orbicularis and Lutjanus indicus were recorded for the first time in Qatari waters. Several trends were uncovered in the vertical distribution of the fish community; most species were observed between 20 and 50 m depth and fish abundance decreased towards the bottom, with the highest abundances recorded in the upper layers, i.e. down to 40 m depth. Vertical variation in fish diversity, however, was generally not accompanied by differences in vertical movements. Carnivores and invertivores were the dominant trophic groups, being found at each depth range from surface to seabed. The functional indices showed no significant differences between water depths or diel cycles. The study demonstrates that oil platforms represent a hotspot of fish diversity and interesting sites for studying fish communities, abundance and behaviour.     

Life history traits and temporal trends of abundance of the orange-spotted trevally (Carangoides bajad) from Saudi waters of the Gulf

In this study we lay the groundwork for sustainability-oriented fisheries management, by estimating parameters the life history of orange-spotted trevally Carangoides bajad as well as trends of abundance in coral-reef habitats. We observed a new record of maximum size of 720 mm fork length. Carangoides bajad is a moderately long-lived (14 years) and slow-growing (K = 0.085 year⁻¹) carangid species, closer to a K-selection species, with higher vulnerability to fishing and lower rates of recovery when the population level is low. Growth and biological composition in terms of length and age categories do not differ between the sexes, but females become mature faster. Reproductively active months (May–August) overlapped with those from Emirati waters further south. The abundance index showed a pronounced drop during 1990–1993, possibly in connection with habitat deterioration during the Gulf War (1990–1991) oil spill. The index increased gradually from 1994 and has fluctuated close to the reference level of 1985 up to the present. Considering the findings of large-sized and old-age individuals and abundance index from coral reefs close to its level three decades back, the C. bajad stock in the western part of The Gulf appears to be in healthy exploitation status despite growing harvesting rates.     

Status and management of Atlantic sturgeon, Acipenser oxyrinchus, in North America

The Atlantic sturgeon, Acipenser oxyrinchus, consists of two subspecies distributed along the Atlantic coast of North America from Labrador to the east coast of Florida (Atlantic sturgeon subspecies – A. o. oxyrinchus) and along the Gulf of Mexico from Florida Bay, Florida to the mouth of the Mississippi River (Gulf sturgeon subspecies – A. o. desotoi). The species has been exploited throughout its range with landings peaking around the turn of the 20th century followed by drastic declines shortly thereafter. During recent years, landings in Canadian waters have increased substantially (approximately 129 metric tons in 1993) while in the United States landings are more controlled or prohibited (approximately 22–24 metric tons in 1993). Recently, the Atlantic States Marine Fisheries Commission developed a Fishery management plan for Atlantic sturgeon, and the United States Fish & Wildlife Service and Gulf States Marine Fisheries Commission drafted a Gulf Sturgeon Recovery/Management Plan. Fishery managers in Canada are in the process of establishing more stringent fishery regulations for sturgeon. Thus, the impact on populations due to harvesting should be substantially reduced. Current research focus includes: life history and population status studies, stock delineation, and development of culture and stock enhancement techniques. Implementation of the findings of such studies may be helpful in the restoration of depleted stocks.