Seasonal occurrence and vertical distribution of appendicularians in Toyama Bay, southern Japan Sea

To investigate seasonal variation in the community structureof appendicularians, vertical hauls (0–500 m) with a Norpacnet were made at an offshore station in Toyama Bay at intervalsof 2–4 weeks from February 1990 to January 1991. Additionalsamples were collected with MTD nets at 12–17 differentdepth layers between the surface and a depth of 600–700m at the same position in June, September and December 1986,and March 1992, to examine the vertical distribution of appendicularians.Twenty-one species (including two unidentified species) belongingto five genera were found, and the dominant species were dividedinto three groups by their occurrence period. Oikopleura longicauda,Fritillaria borealis f. typica and F. borealis f. sargassi occurredthroughout most of the year. Fritillaria pellucida, O. fusiformisand O. rufescens were found in summer and autumn. Oikopleuradioica was found in spring and winter. Oikopleura longicaudawas overwhelmingly the most abundant species throughout theyear. This species was always distributed in the upper 100 mdepth, with a peak at a depth of 0–50 m that correspondedto the peak of chlorophyll a concentration during the day andnight in all seasons. The day–night vertical distributionpatterns of F. borealis f. typica, F. pellucida, O. fusiformisand O. rufescens were similar to that of O. longicauda. Seasonalvariations in abundance of appendicularians are considered tobe the result of biological factors rather than physical factorssuch as temperature and salinity. In particular, O. dioica seemsto be affected by food availability.     

Vertical distribution and abundance of mesoplanktonic medusae and siphonophores from the Weddell Sea,Antarctica

The composition, abundance and vertical distribution of mesoplanktonic cnidarians collected along a transect across the Weddell Sea have been analysed. The transect was characterized by a thermocline, approximately between 200 and 100 m, which deepened significantly towards the shelf edges. In total, 10 species of medusae and 18 species of siphonophores were identified. The most abundant medusae were Pantachogon scotti (up to 11,671 specimens/1,000 m³) and Arctapodema ampla (up to 960 specimens/1000 m³). The most abundant siphonophores were Muggiaea bargmannae (up to 1,172 nectophores/1,000 m³) and Dimophyes arctica (up to 230 nectophores/1,000 m³). Five assemblages of planktonic cnidarians were distinguished: (a) epipelagic species located in and above the thermocline; (b) epi- and upper mesopelagic species located in, above and just below the thermocline; (c) epi- and mesopelagic species located in and below the thermocline; (d) mesopelagic species; (e) lower mesopelagic species. Differences in the depth distribution of the various species gave rise to a clear partitioning of the mesoplanktonic cnidarian population throughout the water column. This vertical partitioning was related to the existence of a thermocline, the structure of the water column and the vertical distribution of prey.     

Seasonal change in the abundance of Synechococcus and multiple distinct phylotypes in Monterey Bay determined by rbcL and narB quantitative PCR

Synechococcus is a cosmopolitan marine cyanobacterial genus, and is often the most abundant picocyanobacterial genus in coastal waters. Little is known about Synechococcus seasonal dynamics in coastal zones highly impacted by upwelling. This was investigated by collecting seasonal samples from an upwelling-impacted Monterey Bay (MB) monitoring station M0, in parallel with measurements of oceanographic conditions during 2006-2008. Synechococcus abundances were determined using quantitative PCR (qPCR) assays and flow cytometry (FCM). A new qPCR assay was designed to target dominant Synechococcus in MB using the rbcL gene, while previously designed assays targeted distinct phylotypes (called narB subgroups) with the narB gene. The rbcL qPCR assay successfully tracked abundant Synechococcus in MB, accounting for on average 89% (± 57%) of FCM-based counts. Annual spring upwelling caused decreases in Synechococcus and narB subgroup abundances. Differences in narB subgroup abundance maxima and abundance patterns support the view that subgroups differ in their ecologies, including subgroup D_C1, which seems to specifically thrive in coastal waters. Correlations between narB subgroup abundances and measured environmental variables were similar among the subgroups. Therefore, non-measured environmental factors (e.g. metals, mortality) likely had different influences on subgroups, which led to their distinct abundance patterns at M0.     

Monterey Bay phytoplankton I. Seasonal cycles of phytoplankton assemblages

Netplankton collections from shallow-water stations in MontereyBay, California were examined for 1976 and 1977. The predominatingphytoplankton forms were neritic diatom species. Recurrent speciesgroups were identified using Fager's regroup analysis and theirdistributions related to hydrographic seasons. Neritic groupswere relatively more abundant during the Davidson Current andupweiling periods; however, many of the species were presentthroughout much of the year. The appearance of oceanic groupsand species was seasonal and associated with advective events. One neritic species group was of overwhelming numerical importancebut within the group conspicuous changes in relative abundanceof phytoplankton populations occurred seasonally among speciesfrom this group. This group appears to be composed of residentspecies and may be locally retained as vegetative cells or benthicresting stages. Species cycles in Monterey Bay may be regardedas largely the result of suc-cessional changes or cycles ofautochthonous species, while species introduced by adjectiveprocesses appear to be of minor importance. The study has suggested that the presence of species in a ‘seedpopulation’, either as vegetative cells or benthic restingstages, may be important as the growth rate of the species inunderstanding and predicting composition and relative abundancein coastal phytoplankton assemblages.     

Seasonal and interannual variation in distribution and population abundance of the shrimp Crangon franciscorum in San Francisco Bay

Shrimp are an important component of the San Francisco Bay biota, both as predators on benthic fauna, and as a food source for predatory fish. Of three common species in the bay, Crangon franciscorum is the most abundant. The bay is predominantly a nursery area for maturing shrimp of this species. During the main reproductive period in the early spring, ovigerous females and planktonic larvae are in most years centered outside the bay in the nearshore ocean, although both are also present in the bay. Juveniles move into both the southern reach and the northern reach shortly after settling, and landward-flowing bottom currents are possibly instrumental in this migration. The seasonal cycle of shrimp abundance in the bay, dominated by this spring immigration of newly settled juveniles, is characterized by a progressive migration of the growing shrimp up the estuary coincident with upstream penetration of higher salinity water during summer. Differences in abundance and distribution between the years 1980, 1981, and 1982 suggest that the level of river discharge and accompanying salinity regime are important controlling factors in the distribution, recruitment levels, and subsequent survival and growth of C. franciscorum in the San Francisco Bay.     

Seasonal abundance and distribution of Caridea larvae in Isafjord-deep, north-west Iceland

The abundance and distribution of Candea larvae was studiedin Ísafjord-deep, north-west Iceland, at approximatelymonthly intervals from February 1987 to February 1988 Zooplanktonsampling was made at nine stations along the length of the fjord,while temperature and chlorophyll a measurements from one ofthe stations are also presented Larvae of six species occurredin the samples, Eualus pusiolus and Pandalus borealis were mostnumerous, constituting 62 8 and 25 9% of the larvae respectively.The other species were, in declining order of abundance, Pandalusmontagui, Spirontocaris spp. (S spinus and s lilljeborgii) andSabinea septemcarinata. Eualus pusiolus was of highest abundancein the outer and middle parts of the fjord, while P.borealiswas most common in the middle and inner parts The onset of hatchingof all species in April–May appeared closely linked tothe phytoplankton spring bloom, while the temperature in thefjord was by then near the annual low (2–3°C). Exceptfor E pusiolus, of which a small part of the population produceda second brood during the summer, most of the larvae had disappearedfrom the plankton by the middle of August The monthly carapacegrowth of P.borealis larvae during the summer months was estimatedto be 1.0 mm.     

Influence of teleost abundance on the distribution and abundance of sharks in Florida Bay, USA

Understanding the factors that influence the distribution and abundance of predators, including sharks, is important for predicting the impacts of human changes to the environment. Such studies are particularly important in Florida Bay, USA where there are planned large-scale changes to patterns of freshwater input from the Everglades ecosystem. Studies of many marine predators suggest that links between predator and prey habitat use may vary with spatial scale, but there have been few studies of the role of prey distribution in shaping habitat use and abundance of sharks. We used longline catches of sharks and trawls for potential teleost prey to determine the influence of teleost abundance on shark abundance at the scale of regions and habitats in Florida Bay. We found that shark catch per unit effort (CPUE) was not linked to CPUE ofteleosts at the scale of sampling sites, but shark CPUE was positively correlated with the mean CPUE for teleosts within a region. Although there does not appear to be a strong match between the abundance of teleosts and sharks at small spatial scales, regional shark abundance is likely driven, at least partially, by the availability of prey. Management strategies that influence teleost abundance will have cascading effects to higher trophic levels in Florida Bay. Electronic Supplementary Material is available for this article at     

莱州湾强壮滨箭虫种群数量及个体大小季节分布

基于2011年5月至2012年4月(12月和翌年1—2月冰期除外)在渤海莱州湾逐月采集的数据资料,分析莱州湾强壮滨箭虫丰度空间分布和体长的季节变化,估算其生产力和摄食率,以掌握其种群动态特征,为评价该种在莱州湾生态系统结构功能中地位提供参数和依据。结果显示:强壮滨箭虫丰度和生物量年变化曲线为双峰型,最高峰出现于5月,次高峰出现于8—9月;4 mm和15 mm体长的个体分别是丰度和生物量的主要贡献者。生产力估值为0.25 mg C m~(-3)d~(-1),摄食率估值为0.88 mg C m~(-3)d~(-1)。种群月均体长以3—4月最高(10 mm)、5月和11月最低(5 mm);月均体长与月表层水温、盐度呈负相关。春季5月、夏季7—8月和秋季10—11月中,小型个体丰度所占的比例较高,应为种群数量增长期。各月的体长频数分布可分辨出平均体长5mm(Cohort Ⅰ)、介于5—10 mm(Cohort Ⅱ)和10 mm(Cohort Ⅲ)的3个同生群。Cohort Ⅲ和Cohort I高丰度区的表层水温和盐度分别介于15—17℃和29—32。Cohort Ⅲ基本不出现于水温大于24℃的站位,其丰度与水温呈显著负相关。Cohort Ⅰ基本不出现于水温低于11℃的站位,其丰度与水温呈显著正相关。Cohort Ⅱ高丰度区的表层水温和盐度为26—27℃和30—32。由上推测强壮滨箭虫发生明显体型更替的水温阈值应不超过15—17℃。     

长江口及邻近海域浮游磷虾类数量和分布的季节特征

根据2002～2003年长江口29°00′～32°00′N、122°00′～123°30′E海域4个季节的海洋调查,运用定量、定性方法,探讨长江口邻近海域浮游磷虾类总丰度的季节变化特征以及与渔场的关系,丰度的季节差异与水团的关系,分析了优势种的数量变动、对磷虾类的贡献及对环境的适应情况,并与东海外海的生态特征作了比较。结果表明,长江口及邻近海域磷虾类丰度季节变化主要受温度的影响,平面分布变化与盐度有关。平均丰度夏季最高（10.46ind/m3）,冬季最低（0.32ind/m3）。本次调查共发现8种,优势种为中华假磷虾（Pseudeuphausia sinica）、太平洋磷虾（Euphausia pacifica）和小型磷虾（Euphausia nana）,其中中华假磷虾四季皆为优势种,太平洋磷虾是春、秋和冬季的优势种,小型磷虾仅仅是春秋季的优势种。中华假磷虾在春、夏和冬季对总丰度的贡献率较高,并占绝对优势,其更适应夏季咸淡水交错水域的环境,而太平洋磷虾和小型磷虾更适应东海近海暖温高盐环境。长江冲淡水势力强弱和中华假磷虾的数量对磷虾类时空分布有重要影响,中华假磷虾对咸淡水环境的适应则是影响该种数量变化的另一个重要原因。     

Seasonal variations in abundance, development and vertical distribution of Calanus finmarchicus, C. hyperboreus and C. glacialis in the East Icelandic Current

The seasonal variation in abundance and development of Calanusfinmarchicus, Calanus hyperboreus and Calanus glacialis in relationto hydrography and chlorophyll (Chl) a was studied in the Arcticwaters of the East Icelandic Current to the north-east of Icelandfrom March 1995 to February 1996. The sampling was carried outat approximately monthly intervals on a transect of five stationsextending from 67°00'N, 13°55'W to 68°00'N, 12°40'W.In April, May and June, vertical distribution was also investigated.Spring warming of the surface waters began in May, with maximumtemperatures recorded in August (~5°C, mean for uppermost50 m). Below 75 m, temperature remained at <0°C throughoutthe year. The spring bloom of phytoplankton started in earlyMay and the highest Chl a concentrations were measured duringlate May to early June (~1 mg Chl a m^-3). Calanus finmarchicusdominated in terms of numbers (~75%), while C. hyperboreus dominatedbiomass (~76%). Calanus glacialis occurred only in low numbers(~1%) and was only a small portion of biomass (~0.7%). The abundanceof all species was low during the winter and peaked once duringsummer: C. finmarchicus in July (~16 000 ind. m^-2) and C. glacialisand C. hyperboreus in June (~370 and ~7700 ind. m^-2, respectively).The biomass of C. finmarchicus had two maxima, in April (~1.9g m^-2) and July (~1.5 g m^-2), while C. hyperboreus peaked inJune (~12.3 g m^-2). Calanus finmarchicus was estimated to spawnin early May at about the start of the spring bloom, while C.hyperboreus spawned prior to the spring bloom, in late Februaryto early March. On the basis of copepod stage distribution,C. finmarchicus was considered to have a 1-year life cycle andC. hyperboreus at least a 2-year life cycle.     

Trends in Dinophysis abundance and diarrhetic shellfish toxin levels in California mussels (Mytilus californianus) from Monterey Bay,California

Diarrhetic shellfish toxins (DSTs) are produced by the marine dinoflagellate, Dinophysis, as well as select species of benthic Prorocentrum. The DSTs can bioaccumulate in shellfish and cause gastrointestinal illness when humans consume high levels of this toxin. Although not routinely monitored throughout the U.S., recent studies in Washington, Texas, and New York suggest DSTs may be widespread throughout U.S. coastal waters. This study describes a four-year time series (2013–2016) of Dinophysis concentration and DST level in California mussels (Mytilus californianus) from Santa Cruz Municipal Wharf (SCMW) in Monterey Bay, California. Results show a maximum Dinophysis concentration of 9404 cells/L during this study and suggest Dinophysis persists as a member of the background phytoplankton community throughout the year. In California mussels, DSTs were found at persistent low levels throughout the course of this study, and exceeded the FDA guidance level of 160 ng/g 19 out of 192 weeks sampled. Concentrations of Dinophysis alone are a positive but weak predictor of DST level in California mussels, and basic environmental variables (temperature, salinity, and nutrients) do not sufficiently explain variation in Dinophysis concentration at SCMW. This study demonstrates that Dinophysis in Monterey Bay are producing DSTs that accumulate in local shellfish throughout the year, occasionally reaching levels of concern.     

Pelagic fish distribution and ontogenetic vertical migration in common mesopelagic species off Lützow-Holm Bay (Indian Ocean sector,Southern Ocean) during austral summer

The horizontal and vertical distributions of fish were examined off Lützow-Holm Bay in the Indian Ocean sector of the Southern Ocean during midnight sun in January 2005. Fish were sampled from six discrete depth layers (0–2,000 m). The most abundant fish in layers from the surface to 200 m were larval stages of Electrona antarctica and Notolepis coatsi. In layers from 200 to 2,000 m, fish assemblages were relatively uniform among all stations and were dominated by E. antarctica (juvenile–subadult), Cyclothone microdon, and Bathylagus antarcticus. Cluster analysis revealed three epipelagic communities related to water temperature and salinity. An ontogenetic habitat shift to deeper layers was apparent for E. antarctica, N. coatsi, and B. antarcticus. Preferences for warm waters were observed in E. antarctica (larvae) and N. coatsi (preflexion to flexion larvae), although they were distributed across a broad range of temperature and salinity in epipelagic zones.     

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.     

Effect of water clarity on the distribution of marine birds in nearshore waters of Monterey Bay, California

ABSTRACT.   The distribution of marine birds relative to water clarity was examined in the nearshore waters of Monterey Bay, California. I conducted nine at-sea surveys in 1999 and 2000 and simultaneously recorded water clarity and the density of five taxa of marine birds. Among plunge-divers, Forster's Terns ( Sterna forsteri ) occurred more frequently than expected over turbid water (<2.5 m Secchi depth) and, among pursuit-diving species, Brandt's Cormorants ( Phalacrocorax penicillatus ) occurred most often in the clearest water available (>5 m Secchi depth). Turbidity in Monterey Bay may be caused by suspended organic matter, including phytoplankton, during summer and fall. Forster's Tern may prefer such areas because small fish are likely to occur near this potential food source. Brandt's Cormorants probably rely on vision to catch fish near the bottom and turbid water may reduce available light and limit visual acuity. The distribution of Brown Pelicans (Pelecanus occidentalis ), Western/Clark's Grebes (Aechmophorus occidentalis/clarkii ), and Marbled Murrelets ( Brachyramphus marmoratus ) did not appear to be influenced by turbidity levels, indicating that some seabirds use marine habitats with a wide range of water clarities.     

Note on the occurrence of Pseudo-nitzschia australis and domoic acid in squid from Monterey Bay, CA (USA)

Over the past decade diatom blooms of domoic acid (DA)-producing Pseudo-nitzschia spp. have been responsible for numerous marine mammal and bird mortalities in Monterey Bay, CA. One possible toxin vector is the market squid, Loligo opalescens, a small pelagic mollusk that plays an important role in the near-shore food web of the California Current ecosystem as a favored vertebrate prey species. This study examined the trophic link between toxic Pseudo-nitzschia and L. opalescens using toxin and stomach content analyses of animals collected from Monterey Bay, CA in 2000. Receptor binding assay data (confirmed by tandem mass spectrometry), demonstrated the presence of DA in squid during a toxic Pseudo-nitzschia event, with P. australis frustules observed in stomach samples. Though DA levels were low (<0.5 μg DA g⁻¹ tissue) in L. opalescens during the study period, it is now clear that this potent neurotoxin can occur in squid and is likely delivered through its krill prey species, which are known to retain DA after feeding on toxic Pseudo-nitzschia. Our findings suggest that further study of the relationship between Pseudo-nitzschia blooms and DA contamination of squid is warranted to better evaluate the potential health risk to humans and wildlife associated with this major commercial seafood species and important prey item.     

Quantitative distribution of presumptive archaeal and bacterial nitrifiers in Monterey Bay and the North Pacific Subtropical Gyre

The recent isolation of the ammonia-oxidizing crenarchaeon Nitrosopumilus maritimus has expanded the known phylogenetic distribution of nitrifying phenotypes beyond the domain Bacteria. To further characterize nitrification in the marine environment and explore the potential crenarchaeal contribution to this process, we quantified putative nitrifying genes and phylotypes in picoplankton genomic libraries and environmental DNA samples from coastal and open ocean habitats. Betaproteobacteria ammonia monooxygenase subunit A (amoA) gene copy numbers were low or undetectable, in stark contrast to crenarchaeal amoA-like genes that were broadly distributed and reached up to 6 x 10(4) copies ml(-1). Unexpectedly, in the North Pacific Subtropical Gyre, a deeply branching crenarchaeal group related to a hot spring clade (pSL12) was at times abundant below the euphotic zone. Quantitative data suggested that the pSL12 relatives also contain archaeal amoA-like genes. In both coastal and open ocean habitats, close relatives of known nitrite-oxidizing Nitrospina species were well represented in genomic DNA libraries and quantitative PCR profiles. Planktonic Nitrospina depth distributions correlated with those of Crenarchaea. Overall, the data suggest that amoA-containing Crenarchaea are more phylogenetically diverse than previously reported. Additionally, distributional patterns of planktonic Crenarchaea and Nitrospina species suggest potential metabolic interactions between these groups in the ocean's water column.     

兴化湾浮游动物群落季节变化和水平分布

兴化湾为福建北部最大的海湾,于2006年对该海湾浮游动物群落进行了四季9个站位的调查。共检出浮游动物及幼虫124种,其中春季42种,夏季89种,秋季71种,冬季20种;分属近岸暖温、近岸暖水和广布外海3个生态类群;优势种15种,春季以水母和桡足类占优势,夏季以水母占优势,秋季以水母、桡足类和箭虫占优势,冬季则以桡足类占优势。不同季节兴化湾浮游动物生物量湿重和丰度水平分布特征变化明显,并与温度和盐度呈显著相关。聚类分析显示兴化湾浮游动物群落夏季类群和秋季类群相似度较高;各季节水平分布基本可分为湾口区和湾内区两大类群。与20世纪80年代相比,尽管本次调查浮游动物群落没有表现出显著差异,但随着电厂等大规模工程的投产,兴化湾海域生态系统健康面临着极大威胁,其环境压力需引起持续关注。