From the Cover: Fishing amplifies forage fish population collapses

Forage fish support the largest fisheries in the world but also play key roles in marine food webs by transferring energy from plankton to upper trophic-level predators, such as large fish, seabirds, and marine mammals. Fishing can, thereby, have far reaching consequences on marine food webs unless safeguards are in place to avoid depleting forage fish to dangerously low levels, where dependent predators are most vulnerable. However, disentangling the contributions of fishing vs. natural processes on population dynamics has been difficult because of the sensitivity of these stocks to environmental conditions. Here, we overcome this difficulty by collating population time series for forage fish populations that account for nearly two-thirds of global catch of forage fish to identify the fingerprint of fisheries on their population dynamics. Forage fish population collapses shared a set of common and unique characteristics: high fishing pressure for several years before collapse, a sharp drop in natural population productivity, and a lagged response to reduce fishing pressure. Lagged response to natural productivity declines can sharply amplify the magnitude of naturally occurring population fluctuations. Finally, we show that the magnitude and frequency of collapses are greater than expected from natural productivity characteristics and therefore, likely attributed to fishing. The durations of collapses, however, were not different from those expected based on natural productivity shifts. A risk-based management scheme that reduces fishing when populations become scarce would protect forage fish and their predators from collapse with little effect on long-term average catches.Forage fish are small pelagic fish, such as herrings, anchovies, and sardines, that provide multiple benefits to people and marine food webs. These species support the largest fisheries in the world, accounting for 30% of global fisheries landings by weight and benefiting aquaculture and livestock industries through the production of fish meal and fish oil (1). At the same time, these species are important for marine food webs, because they provide a key linkage from lower trophic-level planktonic species to upper trophic-level predators, such as large fish, seabirds, and marine mammals (2–4). These predators also have economic value through fisheries (2), tourism (5), or nonmarket existence values (6). Collapses of forage fish populations, which have been frequent (7, 8), can, therefore, generate widespread ecological effects (9–11). Because of these concerns, there is a growing movement to develop and apply robust management approaches to forage fisheries to avoid the risk of fisheries-induced stock collapses and attendant ecological consequences (11, 12).One of the principal challenges in assessing the ecological consequences of forage fish fisheries is that these stocks undergo large cyclical fluctuations in abundance (13, 14) (Fig. 1). Fishing can potentially exacerbate naturally caused collapses, because shifts in populations’ spatial distributions coupled with fish schooling behavior allow fisheries to be economically viable, even when abundance is low (7, 15). Because of these fluctuations, standard static reference points used to judge stock status [e.g., unfished biomass (biomass that maximizes long-term sustainable yield)] have little meaning for the management of forage fish stocks. Most reference points are based on a presumed relation between population production and population biomass, but such a relationship rarely exists among these populations (Fig. S1). Moreover, these fluctuations greatly reduce our ability to ascertain effects of fishing on stock dynamics (16), and by extension, effects of fishing on dependent predators. Some have concluded that fishing acts primarily to accelerate population collapses that were destined to occur because of natural processes (7). To date, it has not been possible to determine whether fishing also makes collapses more frequent, more severe, or more prolonged.Open in a separate windowFig. 1.Examples of forage fish biomass trends showing magnitudes and characteristics of population fluctuations. Dotted lines denote the long-term mean biomass for each stock, and horizontal and vertical bars show time and biomass scale (expressed as a ratio of annual biomass to mean biomass), respectively. Time series are not aligned according to actual start and end date; β is the Fourier spectral scaling exponent, where variance scales with frequency as f ^−β. Five stocks show the range of population fluctuations from extreme long- (Tsushima Strait Pilchard) to short-term (Atlantic Menhaden) variability. Across all 40 stocks for which there were sufficiently long biomass time series to estimate β, the average coefficient of variation (CV) and β were 0.5 and 1.9, respectively. For comparison, a common decadal scale environmental index, the Pacific Decadal Oscillation (33), has β near 1.0.Here, we contribute to understanding ecological consequences of forage fish fisheries to ask how fishing has affected population characteristics that are most relevant for dependent predators. Predators are most sensitive to changes in forage fish abundance when forage abundance is low (9), and therefore, we focus on the effects of fishing with respect to the magnitude (scale of fluctuation), frequency (proportion of stocks at low abundance), and duration (number of years until recovery) of stock collapse. We compiled time series of population biomass and fisheries catches on stocks around the globe from stock assessments, restricting our analysis to 55 stocks with a time series that spanned at least 25 y (Table S1). Forage fish stocks used in this analysis included anchovies, capelin, herrings, mackerels, menhaden, sand eels, and sardines, which since 2000, supported average annual catches of 17 million tons y⁻¹ and comprised 65% of global forage fish catches (17).     

Appraisal of sedimentary alkenones for the quantitative reconstruction of phytoplankton biomass

Marine primary productivity (PP) is the driving factor in the global marine carbon cycle. Its reconstruction in past climates relies on biogeochemical proxies that are not considered to provide an unequivocal signal. These are often based on the water column flux of biogenic components to sediments (organic carbon, biogenic opal, biomarkers), although other factors than productivity are posited to control the sedimentary contents of the components, and their flux is related to the fraction of export production buried in sediments. Moreover, most flux proxies have not been globally appraised. Here, we assess a proxy to quantify past phytoplankton biomass by correlating the concentration of C₃₇ alkenones in a global suite of core-top sediments with sea surface chlorophyll-a (SSchla) estimates over the last 20 y. SSchla is the central metric to calculate phytoplankton biomass and is directly related to PP. We show that the global spatial distribution of sedimentary alkenones is primarily correlated to SSchla rather than diagenetic factors such as the oxygen concentration in bottom waters, which challenges previous assumptions on the role of preservation on driving concentrations of sedimentary organic compounds. Moreover, our results suggest that the rate of global carbon export to sediments is not regionally constrained, and that alkenones producers play a dominant role in the global export of carbon buried in the seafloor. This study shows the potential of using sedimentary alkenones to estimate past phytoplankton biomass, which in turn can be used to infer past PP in the global ocean.

Global carbon distribution between the ocean and the atmosphere regulates global climate on Earth. This distribution is primarily controlled by marine primary productivity (PP) and phytoplanktonic organisms, which transforms atmospheric CO₂ into organic matter. Only a fraction of this produced organic matter is exported to the deep ocean. Global models estimate that 48 PgC·y⁻¹ are produced in ocean surface waters (1), while 6 PgC·y⁻¹ (2) are exported out from the photic zone and 0.15 PgC·y⁻¹ are buried in sediments (3). Exported organic carbon is out of contact with the atmosphere on decadal-to-millennial timescales or longer once is buried in the seafloor, which exerts a major control on global climate by regulating the partial pressure of atmospheric CO₂ (4). Hence, estimating marine PP, export, and burial productivity changes during past key climatic periods (e.g., glacial–interglacial transitions) is essential to understand our present climate and predict its evolution in the future.To infer past PP, a range of proxies based on the fluxes of biogenic components are available (5–7). As flux proxies, they are related to changes in past export productivity, which are assumed to be proportional to surface PP in paleoreconstructions. However, depositional factors such as oxygen or ballasting effect are thought to be important in controlling organic matter export from the upper water column to sediments (8–10), and thus, sedimentary organic proxies concentration. The relative weights of the factors that control the spatial variability of organic matter concentration in sediments are still unconstrained, which leads to some uncertainty on the applicability of organic matter proxies to infer PP (7). Consequently, available proxies are sometimes interpreted to infer either changes in PP or depositional conditions (11).One of the common approaches to reconstruct PP relies on the measurement of C₃₇ di- and tri- unsaturated methyl ketones (i.e., C₃₇ alkenones) concentrations or fluxes in sediments (12–18). These organic molecules are biomarkers of the ubiquitous coccolithophore Emiliania huxleyi, which is the principal source of alkenones and the most abundant coccolithophore in the modern pelagic ocean (19–24). Geophyrocapsa oceanica and other coccolithophoral species from the same genera are also considered important alkenones producers nowadays (20).In this study, we evaluate the potential use of sedimentary C₃₇ alkenones content to infer past phytoplankton biomass at a global scale through the comparison of their spatial variability in a global compilation of core-top sediments with sea surface chlorophyll-a (SSchla) (Fig. 1). This is the primary pigment of photosynthesis and is present in all photosynthetic phytoplankton species. Its concentration in surface waters is commonly used as an indicator of phytoplankton biomass and to infer PP (25, 26). On a global scale, its concentration in surface waters is estimated by remote sensing (27). We also assess the effect of oxygen on the spatial accumulation of alkenones in sediments by comparing its concentration in bottom waters with alkenones abundance on a global scale.Open in a separate windowFig. 1.Global core-top sediments distribution. Lines delineate distinct biogeochemical regions defined on the basis of phytoplankton community, temperature, and nutrient concentration (44). SA, subarctic; SO, Southern Ocean; ST, subtropics; T, tropics.     

海洋微生物次级代谢产物抗菌作用研究进展

海洋微生物次级代谢产物种类繁多,具有丰富的结构多样性和不同的抗菌功能。其中以抗菌活性物质最为突出,已经成为近年来新药筛选的重要资源,在药品开发应用中具有良好的发展前景。本文结合近年关于海洋微生物次级代谢产物的报道,分析海洋微生物次级代谢产物的结构和功能;并对海洋微生物次级代谢产物在抗菌方面的作用及其抗菌作用机制的研究进展进行总结。     

陆军某部新兵濒海训练亚健康状态调查分析

目的探讨濒海训练期间陆军某部新兵亚健康罹患率及其相关因素,为找出切实可行的干预对策提供依据。方法采取自身对照,分别对参训新兵训练前、训练中(训练开始后的20 d)和训练结束后进行"康奈尔医学指数量表(CMI)"调查分析,确定其中亚健康状态发生率及程度。结果海训过程中的亚健康状态及心理障碍发生率显著高于海训前及训练结束后,参加海训的新兵的亚健康罹患率高于未参加海训的新兵(P<0.05);此外,高中学历的亚健康发生率显著高于初中、大专及大专以上学历士兵。结论高强度的濒海训练是诱发亚健康状态的重要因素,但参训士兵的应对方式对个体的亚健康状态也有极大影响,应对方式和心理健康水平密切相关;文化程度及对海训的顾虑程度也是影响亚健康状态的相关因素。     

海洋天然产物治疗心血管疾病作用机制的研究进展

海洋中复杂的生存条件造就了海洋天然产物区别于陆地天然产物的独特结构和多样的生理活性。从海洋生物中提取的活性物质大多具有良好的抗炎、抗肿瘤、免疫调节和治疗心血管疾病等作用。心血管疾病又称循环系统疾病,在我国的患病率和死亡率不断增加,成为城乡居民致死和致残的首要原因。就近年来海洋天然产物在治疗心血管疾病方面抗血栓形成、改善心功能、抗高血压的作用机制研究进展进行综述。     

A case of transthyretin amyloidosis with myopathy,neuropathy, and cardiomyopathy resulting from an exceedingly rare mutation transthyretin Ala120Ser (c.418G > T,p.Ala140Ser)

Abstract

Senile plaques (SPs) and cerebral amyloid angiopathy (CAA) consisting of β-amyloid (Aβ) are major features in the brain of Alzheimer's disease (AD) patients and elderly humans and animals. In this study, we report the finding of SPs and CAA in an aged sea lion (30 years), which is the first demonstration of AD-related pathological changes in a marine animal. Histologically, SPs were observed at the cerebral cortex, most frequently at the frontal lobe, with two morphologically different types: the small round type and the large granular type. Only the small round SPs were positive for Congo red staining. The SPs were equally immunoreactive to Aβ40 and Aβ42 and were mainly composed of Aβ with an N-terminal pyroglutamate residue at position 3. Amyloid depositions at vessel walls were noted at the meninges and within the parenchyma. Interestingly, double immunofluorescence staining for Aβ40 and Aβ42 showed that the two subtypes were deposited segmentally in different parts of the vessel walls. The lesions observed in the sea lion suggest that Aβ deposition is widely present in various animal species, including marine mammals; however, the peculiar deposits similar to cotton wool plaques and the specific pattern of CAA are characteristic features of this animal.     

Adult and larval traits as determinants of geographic range size among tropical reef fishes

Most marine organisms disperse via ocean currents as larvae, so it is often assumed that larval-stage duration is the primary determinant of geographic range size. However, empirical tests of this relationship have yielded mixed results, and alternative hypotheses have rarely been considered. Here we assess the relative influence of adult and larval-traits on geographic range size using a global dataset encompassing 590 species of tropical reef fishes in 47 families, the largest compilation of such data to date for any marine group. We analyze this database using linear mixed-effect models to control for phylogeny and geographical limits on range size. Our analysis indicates that three adult traits likely to affect the capacity of new colonizers to survive and establish reproductive populations (body size, schooling behavior, and nocturnal activity) are equal or better predictors of geographic range size than pelagic larval duration. We conclude that adult life-history traits that affect the postdispersal persistence of new populations are primary determinants of successful range extension and, consequently, of geographic range size among tropical reef fishes.Geographic range size is a fundamental biogeographic variable that, among other effects (1, 2), strongly influences a species susceptibility to extinction (3, 4). Because most marine organisms disperse as larval propagules transported by ocean currents, it is often assumed that the duration of the larval stage is the fundamental determinant of their dispersal ability, and hence their range size (5, 6). Tropical reef fishes have geographic ranges that vary greatly in size, from a few square kilometers around tiny isolated islands to entire ocean basins (7–9). Given that pelagic larval duration (PLD) also varies greatly among such fishes, from only a few days to many months, the effects of PLD on dispersal potential became an early focus of investigation on general determinants of range size among those fishes and other near-shore marine species (10–12). However, although it has become evident that PLD is unlikely to be a primary determinant of geographic range size (13–16), alternative hypotheses have only recently begun to be considered (9).To expand its geographic range, a species must successfully colonize new areas following the dispersal of its propagules (17). Consequently, attributes other than pelagic dispersal capacity may largely determine how widely reef fishes are distributed geographically (9). Here we assess the relative importance of seven adult and larval traits in influencing geographic range sizes of tropical reef fishes at the global scale. We do so using data from 590 species of tropical reef fishes in 47 families, the largest compilation of such data currently available for any marine group (Dataset S1). Traits directly linked to larval dispersal potential include PLD and spawning mode. Adult traits include maximum body size, schooling behavior, nocturnal activity, use of multiple habitat types, and adult depth range. The adult-biology traits chosen are not directly related to larval dispersal potential, but may influence the propensity for range expansion by affecting the establishment and persistence of new populations, as suggested by a recent study on Atlantic reef fishes (9). For example, schooling (18, 19) and nocturnal activity (20) reduce predation risk and thereby increase the chance of postsettlement survival. Broad habitat use and depth range indicate ecological generality, which is thought to influence establishment success in new environments (21). Finally, body size is linked to both predation risk and ecological generality (22).Evaluation of these hypotheses is challenging because species traits are phylogenetically nonindependent (23) and unevenly distributed among families. Previous studies of dispersal–range-size relationships have controlled for effects of phylogeny, and limits on range-size imposed by ocean-basin size, by separately analyzing subsets of data (7, 16). However, this approach reduces statistical power (23, 24) and the ability to assess the generality of the effects of different factors. Our analysis controls for the nonindependence of shared traits among related species by using linear mixed-effects modeling (LMM) treating family and genus as nested random effects (9, 23). Our analysis includes species from three different regions that vary greatly in maximum (longitudinal or latitudinal) extent: the Indo-Central Pacific (ICP; ∼22,000 km), the tropical Atlantic (TA; ∼12,000 km), and the tropical eastern Pacific (TEP; ∼5,000 km). To control for this variation, we include region and its interactions with other variables as fixed effects in our models. Modeling the data in this way, we are unique in being able to assess the relative importance of various adult and larval traits as determinants of range size among tropical reef-fish, as a group, at the global scale.     

锦州近海海域放射性活度及海生物所致居民的内剂量

本文报道了1988年～1989年锦州近海的海水、海底质和海生物中总α总β, ⁹⁰Sr、¹³⁷Cs, ^6Oco, ¹⁰⁶Ru、²³²Th、²²⁶Ra的放射性活度。在海水和海生物中⁹⁰Sr、¹³⁷Cs稍有增加, 说明海洋环境可能受到了切尔诺贝利事故泄漏物的污染。     

南海多刺网结海绵化学成分的研究

从中国南海多刺网结海绵(Gelliodes spinosella Thielle)的正丁醇可溶物中分离出3个有机化合物,通过UV、IR、~1HNMR、~(13)CNMR和EIMS分析,确定其化学结构分别为:胸腺嘧啶脱氧核苷(1)、苯乙酸(2)和α-苯基丙氨酸(3)。