南海断面春季放射虫残骸的空间分布及其与表层沉积记录对比

放射虫是揭示古海洋环境信息的重要载体。本文采用虎红染色方法,首次揭示了南海典型断面现代放射虫残骸群的空间分布特征,并比较分析现代水体中放射虫残骸群与海底表层沉积物中放射虫化石群的相互关系。结果表明:南海春季放射虫残骸群比较丰富,其丰度一般呈现出随深度增加而增高的趋势,最高值主要出现在75—300m深即位于叶绿素最大值层和活体高峰深度之下;分析发现研究区放射虫残骸丰度的深度分布受到海流的横向输运影响;春季水体和表层沉积物中放射虫属种组成和丰度分布的差异表明,除了现代放射虫具有季节性变化之外,海流的横向传输也是一个很重要的原因。在150—300m水体中除了Cornutella profunda和Cyrtopera laguncula,还发现了Cycladophora davisiana的残骸,推测典型冷水种C.davisiana由于受到径向翻转流的作用,从中深层水被带到了中上层水体中。     

Light and electron microscopic observations of the reproductive swarmer cells of nassellarian and spumellarian polycystines (Radiolaria)

We observed reproductive swarmer cells of the nassellarian and spumellarian polycystine radiolarians Didymocyrtis ceratospyris, Pterocanium praetextum, Tetrapyle sp., and Triastrum aurivillii using light, scanning and transmission electron microscopy. The swarmer cells had subspherical to ovoid or spindle shapes with two unequal flagella tapered to whip-like ends. The cell size was approximately 2.5–5.5 μm long and 1.6–2.2 μm wide, which is significantly smaller than that of the collodarian (colonial or naked) polycystine radiolarians. Transmission electron microscopy revealed that the swarmer cells possessed a nucleus, mitochondria with tubular cristae, Golgi body, and small lipid droplets in the cytoplasm; they also had a large vacuole in which a single crystalline inclusion (approx. 1.0–1.5 μm) that was probably celestite (SrSO₄) was enclosed. The swarmer cells were released directly from the parent cells. At that time, morphological change such as encystment was not observed in the parent cells, and the axopodia remained extended in a period of swarmer reproduction for floating existence. This may have prevented the polycystine swarmers from rapidly sinking down to great depths. Thus, we concluded that the polycystine radiolarians release the swarmer cells into the photic layer in the same way as the symbiotic acantharians.     

Foraminifera and coccolithophorid assemblage changes in the Panama Basin during the last deglaciation: Response to sea-surface productivity induced by a transient climate change

The responses of community assemblages of planktonic and benthonic foraminifera and coccolithophorids to transient climate change are explored for the uppermost 2 m of cores ODP677B (1.2°N; 83.74°W, 3461 m) and TR163-38 (1.34°S; 81.58°W, 2200 m), for the last ∼ 40 ka. Results suggest that the deglaciation interval was a time of increased productivity and a major reorganization of planktonic trophic webs. The succession in dominance between the planktonic foraminifera species Globorotalia inflata, Globigerina bulloides, and Neogloboquadrina pachyderma denote four periods of oceanographic change: (1) advection (24-20 ka), (2) strong upwelling (20-15 ka), (3) weak upwelling (14-8 ka) and (4) oligotrophy (8 ka to present). Strong upwelling for the deglaciation interval is supported by the low Florisphaera profunda/other coccolithophorids ratio and the high percentage abundance of Gephyrocapsa oceanica. Benthonic foraminifera assemblage changes are different in both cores and suggest significant regional variations in surface productivity and/or oxygen content at the seafloor, and a decoupling between surface productivity and export production to the seafloor. This decoupling is evidenced by the inverse relationship between the percentage abundance of infaunal benthonic foraminifera and the percentage abundance of N. pachyderma. The terrigenous input of the Colombian Pacific rivers, particularly the San Juan River, is suggested as a possible mechanism. Finally, the Globorotalia cultrata/Neogloboquadrina dutertrei ratio is used to reconstruct the past influence of the Costa Rica Dome-Panama Bight and cold tongue upwelling systems in the Panama Basin. A northern influence is suggested for the late Holocene (after 5 ka) and the last glacial (before 20 ka), whereas a southern influence is suggested for the 20-5 ka interval. There is a correspondence between our reconstructed northern and southern influences and previously proposed positions of the Intertropical Convergence Zone (ITCZ) after the Last Glacial Maximum (LGM).     

Radiolarian flux in Antarctic waters (Drake Passage,Powell Basin,Bransfield Strait)

Summary The study of radiolarians collected during sediment trap experiments in the Drake Passage, the northern Powell Basin, and the King George Basin of the Bransfield Strait provides new information on the fluxes of radiolarian shells in Antarctic waters, on the annual flux pattern, the species distribution and its ecological significance, and on alteration processes of the radiolarian shells in the water column and at the sediment/water interface. A 28-month monitoring with time-series sediment traps in the Bransfield Strait indicates an annual flux pattern characterized by short-term flux pulses during austral summer, which reach daily fluxes of up to 5 × 10³ shells m^–2 and which account for more than 90% of the total annual flux. The distinct seasonal variations are linked to variations in the sea ice coverage. Other controlling factors are the production of phytoplankton and the impact by zooplankton grazers, e.g., krill. During the summer flux pulses the vertical fluxes of radiolarians range between ca. 3 and 21 × 10⁴ shells m^–2, values that are one or more orders of magnitudes lower than fluxes observed at sites in the tropical and northern high-latitude ocean. Significant lateral transport of radiolarians was documented during the austral summer in the Bransfield Strait by a factor of 10 increase of the radiolarian flux in the lower portion of the water column and the species composition trapped in deeper waters. Radiolarian assemblages associated with pelagic and neritic environments characterized by typical Antarctic taxa (Antarctissa spp.) and a group of species with bipolar distribution (e.g. Plectacantha oikiskos, Phormacantha hystrix), respectively, are distinguished. While the signal of polycystine radiolarians is relatively well recorded in the sediments, the shells of phaeodarians, which were observed at fluxes of up to 1 × 10³ shells m^–2day^–1 in the upper portion of the water column, are almost completely dissolved during settling through the water column.     

Intrusions of the Kuroshio Current in the northern South China Sea affect copepod assemblages of the Luzon Strait

We analyse the influence of the Kuroshio Current on copepod assemblages in the northern South China Sea. The assumption was tested whether predominant current regimes bring marine zooplankton and Copepoda from subtropical and tropical waters to the south of Taiwan. A total of 101 copepod species were identified from 26 families and 48 genera that include Calanoida, Cyclopoida, Harpacticoida and Poecilostomatoida. High copepod abundances in the study area are shown to be caused by both, a year-round Kuroshio Current intrusion and the SW monsoon, prevailing in the South China Sea during summer. Calanus sinicus did not appear in the samples, indicating that there was no cold water mass intrusion in the area during sampling. Both, the intrusion of the Kuroshio Branch Current to the Luzon Strait and the South China Sea circulation may play a more important role in shaping copepod assemblages in the region than hitherto expected. The abundance of copepods was higher above the 50 m isoline than at deeper strata. Species number and the Shannon-Wiener diversity index were higher with increasing depth. Copepod assemblage structure changed with different sampling depth and different sampling areas. Copepod abundance and species richness were higher in the northern South China Sea than in the Kuroshio Current area, and higher at lower latitudes than at higher latitudes. Some indicator species are characteristic for the Kuroshio Current and indicate with others that the study area accomodated water masses from the northern South China Sea as well as from the Kuroshio Current.     

Long-term upwelling evolution in tropical and equatorial Pacific during the last 800 kyr as revealed by coccolithophore assemblages

The coccolithophore assemblages in two ODP Sites (1237 and 1238) are studied in order to reconstruct the paleoenvironmental conditions in the tropical and equatorial Pacific during the last 800 kyr. Both ODP Sites are located in the two most significant upwelling zones of the tropical and equatorial Pacific: Peru and Equatorial upwelling, respectively. The two sites are considered to have had similar evolutions. The coccolith relative abundance, the nannofossil accumulation rate (NAR) and the N ratio (namely, the proportion of < 3 μm placoliths in relation to Florisphaera profunda) allow us to identify three different intervals. Interval I (0.86-0.45 Ma) and interval III (0.22-0 Ma) are related to weak upwelling and weak Trade Winds, as suggested by coccolithophore assemblages with low N ratios. Interval II (0.45-0.22 Ma), characterized by dominant Gephyrocapsa caribbeanica and very abundant “small” Gephyrocapsa and Gephyrocapsa oceanica, is conversely related to intense upwelling and enhanced Trade Winds.     

Solar UV radiation modulates daily production and DNA damage of marine bacterioplankton from a productive upwelling zone (36°S), Chile

In upwelling ecosystems, such as the Humboldt Current system (HCS) off Concepción, the effects of solar radiation on bacterioplankton incorporation rates have been related to previous light acclimation and responses to irradiance. In this paper, we study the daily effect of Photosynthetic Active Radiation (PAR, 400-700 nm) and ultraviolet radiation UVR (280-400 nm) on bacterial secondary production (BSP). We also considered the DNA damage-repair response to solar radiation stress by the induction of cyclobutane pyrimidine dimers (CPDs). Experiments were conducted with natural bacterioplankton assemblages (0.2-0.7 μm) collected off Concepción (36°S), during the austral Spring, October-November, 2004. Surface (0.5 m) and subsurface (80 m) bacterioplankton samples were exposed to different solar radiation treatments for 5-20 h. BSP was estimated by ¹⁴C-leucine and ³H-thymidine incorporation at several time intervals, whereas CPDs accumulation was assessed using immunoassay techniques. During high irradiance periods, BSP was mainly affected by PAR in both surface and subsurface assemblages and, to a lesser, but significant (Tukey < 0.05) extent, by UV-A (320-400 nm) and UV-B (280-320 nm) radiation. Maximum inhibition of BSP in surface waters was 78%; growth rates (μ) and bacterial growth efficiency (BGE) were also low (78% and 66% respectively). Subsurface water assemblages, on the contrary, showed a ∼ 25 fold enhancement of BSP, μ, and BGE. Both types of assemblages had a rapid CPDs accumulation (maximum 60 CPDs Mb^− 1) during high irradiance periods. Recovery of BSP inhibition and DNA damage in surface bacteria was total after sunset and after the night incubation period, resembling pre-exposure levels. Despite subsurface BSP enhancement during day-night exposure, residual DNA damage was detected at the end of the experiment (20 CPDs Mb^− 1) suggesting a chronic DNA damage. Our results represent the worst case scenario (i.e., assemblages receiving surface irradiances as may occur in this upwelling zone) and indicate that surface and subsurface bacterial assemblages in the HCS are both highly sensitive to solar irradiance. However, they showed different responses, with surface bacteria having more effective photorepair mechanisms, and sustaining higher BSP than subsurface assemblages.     

Spatio-Temporal Variability of Copepod Abundance along the 20°S Monitoring Transect in the Northern Benguela Upwelling System from 2005 to 2011

Long-term data sets are essential to understand climate-induced variability in marine ecosystems. This study provides the first comprehensive analysis of longer-term temporal and spatial variations in zooplankton abundance and copepod community structure in the northern Benguela upwelling system from 2005 to 2011. Samples were collected from the upper 200 m along a transect at 20°S perpendicular to the coast of Namibia to 70 nm offshore. Based on seasonal and interannual trends in surface temperature and salinity, three distinct time periods were discernible with stronger upwelling in spring and extensive warm-water intrusions in late summer, thus, high temperature amplitudes, in the years 2005/06 and 2010/11, and less intensive upwelling followed by weaker warm-water intrusions from 2008/09 to 2009/10. Zooplankton abundance reflected these changes with higher numbers in 2005/06 and 2010/11. In contrast, zooplankton density was lower in 2008/09 and 2009/10, when temperature gradients from spring to late summer were less pronounced. Spatially, copepod abundance tended to be highest between 30 and 60 nautical miles off the coast, coinciding with the shelf break and continental slope. The dominant larger calanoid copepods were Calanoides carinatus, Metridia lucens and Nannocalanus minor. On all three scales studied, i.e. spatially from the coast to offshore waters as well as temporally, both seasonally and interannually, maximum zooplankton abundance was not coupled to the coldest temperature regime, and hence strongest upwelling intensity. Pronounced temperature amplitudes, and therefore strong gradients within a year, were apparently important and resulted in higher zooplankton abundance.     

Host-symbiont associations of polycystine Radiolaria: epifluorescence microscopic observation of living Radiolaria

In all 29 polycystine radiolarian species were obtained from surface seawater on May 28, 1999, using a plankton-net at one station (Site 990528; 26°37′18″N, 127°47′35″E) approximately 5 km northwest of Okinawa Island, Japan. In most polycystine radiolarians of the orders Nassellarida and Spumellarida symbiotic algae were observed under light microscopy. The light microscopic (LM) images of the symbionts, however, varied in clarity among individuals because of the variations in microanatomy of the host radiolarian cells. On the other hand, epifluorescence microscopic (EFM) observation easily detected and confirmed the existence of the algal symbionts within the host cytoplasm even in radiolarians such as Dictyocoryne truncatum (Ehrenberg) that include algal symbionts in the depth of the cytoplasm. The chloroplasts of the algal symbionts emitted autofluorescence in ultraviolet irradiation and they appeared red. That is, the autofluorescence images of the chloroplasts can be used to recognize the existence of the algal symbionts within the host radiolarians. Moreover, staining of the symbiont cells with 4′,6-diamido-2-phenylindle permitted visualization of the nucleus in the center of the symbiont cell, confirming the existence of living endosymbiotic algae within the polycystine radiolarians. Both the LM and EFM observations of eight polycystine radiolarian species revealed the specific patterns of various host-symbiont associations. (1) The investigated polycystine radiolarians all possess algal symbionts, except for one species, i.e. Dictyocoryne profunda Ehrenberg. (2) The size of the algal symbionts depends on the radiolarian species. The symbionts are largely classified into two types based on the size of their diameters, i.e. about 8–10 μm for the larger group and about 5 μm for the smaller one. (3) The algal symbionts show a variety of locations within the host radiolarian cytoplasm. The types of distribution of algal symbionts may be a useful characteristic for radiolarian taxonomy.     

Assessment distribution of the phytoplankton community structure at the fishing ground,Banyuasin estuary,Indonesia

The research objective was to describe the distribution of phytoplankton community structure and corelated to the physic-chemical parameters at fishing ground, Banyuasin estuarine waters. The methodology of research was phytoplankton sampling; physicochemical waters parameters data collected such as; dissolved oxygen, pH, temperature, brightness, salinity, current speed, nitrate, and phosphate. Identifications and calculations phytoplankton are based on photography under a light microscope. Data were analyzed by calculated abundance, diversity (H′ index) and dominance (C index), and Principal Component Analysis (PCA). There were 24 species of phytoplankton on the all-observation station grouped in three classes, Bacillariophyceae 91.3%, Dinophyceae 9%, and Cyanophyceae 0.1%. The abundance of phytoplankton species obtained in the range of 666.48 to 184,592.68 cells L^?1, were mostly found in high Chaetoceros affinis and Bacteriastrum furcatum. The distribution of phytoplankton abundance in these waters was found to be more influenced by seawater mass than freshwater. Phytoplankton diversity is considered a moderate category (1.37 < H′ < 2.57), and there were no species of phytoplankton that dominates (C < 0.5). Principal component analyzes showed that waters can be classified based on their physical-chemical characteristics, which were temperature, salinity, pH, transparency, current speed in the south coast around river estuaries, while DO and nutrients on the north coast of the waters. Based on the distribution of phytoplankton abundance is illustrated that the northern part is more potential for fishing area than the southern part with an abundance of phytoplankton >90,000 cells L^?1 and more stable water dynamics.     

Gradients in microbial methanol uptake: productive coastal upwelling waters to oligotrophic gyres in the Atlantic Ocean

Methanol biogeochemistry and its importance as a carbon source in seawater is relatively unexplored. We report the first microbial methanol carbon assimilation rates (k) in productive coastal upwelling waters of up to 0.117±0.002 d⁻¹ (∼10 nmol l⁻¹d⁻¹). On average, coastal upwelling waters were 11 times greater than open ocean northern temperate (NT) waters, eight times greater than gyre waters and four times greater than equatorial upwelling (EU) waters; suggesting that all upwelling waters upon reaching the surface (⩽20 m), contain a microbial population that uses a relatively high amount of carbon (0.3–10 nmol l⁻¹d⁻¹), derived from methanol, to support their growth. In open ocean Atlantic regions, microbial uptake of methanol into biomass was significantly lower, ranging between 0.04–0.68 nmol l⁻¹d⁻¹. Microbes in the Mauritanian coastal upwelling used up to 57% of the total methanol for assimilation of the carbon into cells, compared with an average of 12% in the EU, and 1% in NT and gyre waters. Several methylotrophic bacterial species were identified from open ocean Atlantic waters using PCR amplification of mxaF encoding methanol dehydrogenase, the key enzyme in bacterial methanol oxidation. These included Methylophaga sp., Burkholderiales sp., Methylococcaceae sp., Ancylobacter aquaticus, Paracoccus denitrificans, Methylophilus methylotrophus, Methylobacterium oryzae, Hyphomicrobium sp. and Methylosulfonomonas methylovora. Statistically significant correlations for upwelling waters between methanol uptake into cells and both chlorophyll a concentrations and methanol oxidation rates suggest that remotely sensed chlorophyll a images, in these productive areas, could be used to derive total methanol biological loss rates, a useful tool for atmospheric and marine climatically active gas modellers, and air–sea exchange scientists.     

The vertical distribution of Radiolaria in the waters surrounding Japan

Geographic and vertical distribution patterns of living Radiolaria are closely related to the characters of the water column. We studied living Radiolaria in samples collected at closely spaced depth intervals in the waters surrounding Japan in order to understand their vertical distribution and its controlling factors. Such information is needed to reconstruct past vertical water mass structure. The Japanese Islands are surrounded by the marginal Japan Sea and the North Pacific Ocean, and from approximately 46° N to 26° N. They thus extend across a large latitudinal range and are exposed to a similarly wide range of environmental conditions, inducing the warm Kuroshio, Tsushima, and Tsugaru Currents and the cold Oyashio Current.We performed plankton tows (mesh size 63 mm) from late May to early June 2002 at eight sites, sampling the upper 200 m of the water column, at seven depth intervals.We recognized five radiolarian assemblages: the Upper Surface Assemblage (0–40 m), the Lower Surface Assemblage (40–80 m), the Surface Assemblage (0–80 m), the Subsurface Assemblage (80–200 m), and the Lower Surface–Subsurface Assemblage (40–200 m) groups. Pseudodictyophimus gracilipes and Tetrapyle octacantha (juvenile) show “tropical submergence”, i.e. they live at the surface in high latitudes and at greater depth in low latitudes. Four taxa live at specific temperature and salinity: Acrosphaera spinosa, Larcopyle butschlii, Challengeron diodon, and Stichocorys seriata. Four taxa are associated with characteristic temperatures: Neosemantis distephanus, Arachnocorys umbellifura, Antarctissa sp. 1, and Saccospyris conithorax.     

Dinoflagellate cyst distribution in marine surface sediments off West Africa (17–6°N) in relation to sea-surface conditions, freshwater input and seasonal coastal upwelling

An organic-walled dinoflagellate cyst analysis was carried out on 53 surface sediment samples from West Africa (17–6°N) to obtain insight in the relationship between their spatial distribution and hydrological conditions in the upper water column as well as marine productivity in the study area.Multivariate analysis of the dinoflagellate cyst relative abundances and environmental parameters of the water column shows that sea-surface temperature, salinity, marine productivity and bottom water oxygen are the factors that relate significantly to the distribution patterns of individual species in the region.The composition of cyst assemblages and dinoflagellate cyst concentrations allows the identification of four hydrographic regimes; 1) the northern regime between 17 and 14°N characterized by high productivity associated with seasonal coastal upwelling, 2) the southern regime between 12 and 6°N associated with high-nutrient waters influenced by river discharge 3) the intermediate regime between 14 and 12°N influenced mainly by seasonal coastal upwelling additionally associated with fluvial input of terrestrial nutrients and 4) the offshore regime characterized by low chlorophyll-a concentrations in upper waters and high bottom water oxygen concentrations.Our data show that cysts of Polykrikos kofoidii, Selenopemphix quanta, Dubridinium spp., Echinidinium species, cysts of Protoperidinium monospinum and Spiniferites pachydermus are the best proxies to reconstruct the boundary between the NE trade winds and the monsoon winds in the subtropical eastern Atlantic Ocean. The association of Bitectatodinium spongium, Lejeunecysta oliva, Quinquecuspis concreta, Selenopemphix nephroides, Trinovantedinium applanatum can be used to reconstruct past river outflow variations within this region.     

Diatom taphocoenoses in the coastal upwelling area off South West Africa

The diatom floral composition of 124 sediment samples from the South East Atlantic records the influence of coastal upwelling on sediment composition off South West Africa. Inner shelf samples between 19° and 24°S are rich in diatom valves and the patterns of diatom species distribution in these samples are related to the coastal upwelling process. Comparison with recent phytoplankton data shows that the sediment assemblages preserve many of the important species of the diatom biocoenoses, including Chaetoceros (resting spores), Delphineis karstenii, Thalassiosira eccentrica, and Thalassionema nitzschioides. Delphineis karstenii, a pioneer species in enriched coastal water, occurs nearshore and Chaetoreros resting spores are widespread, with highest relative abundance values in some more offshore samples. The abundance of the Thalassiosira eccentrica group and of Thalassionema nitzschioides in sediment samples in and near Walvis Bay reflects the recurrence of intense upwelling off this part of the coast. An abundance of large centric species has been reported in hydrological conditions characteristic of newly upwelled waters and, correspondingly, Actinocyclus octonarius and some large Coscinodiscus species occur in the sediments in nearshore patches or belts.     

A 350-ky radiolarian record off Lüderitz,Namibia—evidence for changes in the upwelling regime

The study of radiolarian assemblages from Core MD 962086 provides new information on the variability in the upwelling intensity and origin of upwelled water masses over the past 350 ky in one of the major filamentous regions of the Benguela Upwelling System (BUS), located off Lüderitz, Namibia. The use of key radiolarian species to trace the source of upwelled waters, and the use of a radiolarian-based upwelling index (URI) to reconstruct the upwelling intensity represent the first use of radiolarians for paleoceanographic reconstructions in the BUS. These radiolarian-based proxies indicate strongest upwelling during Marine Isotope Stages (MIS) 3, 5, and 8, which compares well with other studies. While during MIS 3 and 8, the radiolarian-based proxies indicate the influx of waters of Southern Ocean origin, they also point to the increased influence of tropical waters during the lower portion of MIS 5. During MIS 2, 4 and 6 the radiolarian assemblages indicate generally lower upwelling intensities, although this signal is complicated by the increased occurrence of organic carbon in the sediments during these intervals. During MIS 2 there appears to be less of an input of Southern Ocean waters to the BUS, although during the also glacial MIS 4 and 6, there is evidence for an increased influence of cold Antarctic waters. The comparison of the results from Core MD 962086 with other studies in the BUS area indicates a non-uniform pattern of upwelling intensity and advection of cold, southern waters into this system during MIS 2. Weaker upwelling signaled by the radiolarian-based proxy in MIS 4 is in contrast to other studies that indicate higher productivity during this time period. In general, the data show that there is a strong spatiotemporal complexity in upwelling intensity in the BUS and that the advection of water into it is not strongly tied to glacial–interglacial variations in climate.     

Gymnoxanthella radiolariae gen. et sp. nov. (Dinophyceae), a dinoflagellate symbiont from solitary polycystine radiolarians

The symbiotic dinoflagellate Gymnoxanthella radiolariae T. Yuasa et T. Horiguchi gen. et sp. nov. isolated from polycystine radiolarians is described herein based on light, scanning and transmission electron microscopy as well as molecular phylogenetic analyses of SSU and LSU rDNA sequences. Motile cells of G. radiolariae were obtained in culture, and appeared to be unarmored. The cells were 9.1–11.4 μm long and 5.7–9.4 μm wide, and oval to elongate oval in the ventral view. They possessed an counterclockwise horseshoe‐shaped apical groove, a nuclear envelope with vesicular chambers, cingulum displacement with one cingulum width, and the nuclear fibrous connective; all of these are characteristics of Gymnodinium sensu stricto (Gymnodinium s.s.). Molecular phylogenetic analyses also indicated that G. radiolariae belongs to the clade of Gymnodinium s.s. However, in our molecular phylogenetic trees, G. radiolariae was distantly related to Gymnodinium fuscum, the type species of Gymnodinium. Based on the consistent morphological, genetic, and ecological divergence of our species with the other genera and species of Gymnodinium s.s., we considered it justified to erect a new, separate genus and species G. radiolariae gen. et sp. nov. As for the peridinioid symbiont of radiolarians, Brandtodinium has been erected as a new genus instead of Zooxanthella, but the name Zooxanthella is still valid. Brandtodinium is a junior synonym of Zooxanthella. Our results suggest that at least two dinoflagellate symbiont species, peridinioid Zooxanthella nutricula and gymnodinioid G. radiolariae, exist in radiolarians, and that they may have been mixed and reported as “Z. nutricula” since the 19th century.     

Radiolarian distribution in the water column,southern Gulf of California,and its implication in thanatocoenose constitution

The geographical and depth distributions of five radiolarian plankton assemblages, defined through Q-mode Factor Analysis of 24 plankton samples, demonstrate a direct correspondence to the distribution of oceanographic water masses in the southern Gulf of California. Two assemblages are associated exclusively with water masses of the mixed-layer, two represent only subsurface water masses, and one is important in both surface and subsurface environments. The Lithomelissa thoracites group and Peridium spinipes are predominant species in water that is formed at the surface of the Guaymas Basin and subsequently is subducted southward into the Carmen Basin. Plagiocantha panarium is the predominant species in upwelled surface water at the Carmen Basin, while Tetrapyle octhacanta and Botryostrobus scutum follow the incursion of the Subtropical Water Mass into the Gulf of California through the Pescadero and Farallon Basins. Druppatractus variabilis and Porodiscus sp. B occur conspicuously in the upper layer of the Pacific Intermediate Water between approximately 400 and 700 m water depth. Statistical correlation between plankton and sediment assemblages supports previous evidence that the radiolarian thanatocoenose in the Gulf of California is composed primarily of species from the surface mixed-layer. Two exceptions to this are observed in the data. First, the upwelling plankton assemblage was not well correlated to the sediment assemblage, and second, input to the sediment during glacial stages appears to be dominated by subsurface forms.     

Zooplankton assemblages as indicators of seasonal changes in water masses in the boundary waters between the East China Sea and the Taiwan Strait

Hydrology and trophic relationships are frequently reported for inducing changes in mesozooplankton communities. This study investigated the distribution and abundance of mesozooplankton in the boundary waters between the East China Sea and the Taiwan Strait. Samples were collected using a NOR-PAC zooplankton net towed horizontally at a depth of 2 m, at eight stations along a transect, in March (spring) and October (autumn) 2005. The abundance of mesozooplankton was significantly higher during autumn than spring. Densities of many groups (e.g., Noctiluca scintillans, pteropods, copepods, mysids, euphausiids, and other larva) increased in October. During both seasons, copepods represented more than 50% of the total zooplankton abundance. Noctiluca scintillans, appendicularians, and Calanus sinicus were dominant in spring, indicating their association with the cold waters of the East China Coastal Current. Appendicularians and N. scintillans were mainly associated with the coastal waters of Taiwan; whereas C. sinicus was concentrated in the offshore waters along the coast of Mainland China. Chaetognaths, Temora turbinata, Acrocalanus spp., and radiolarians were dominant in autumn, showing their association with the warm waters of the Kuroshio Branch Current. Oncaea venusta was relatively abundant during both seasons. Our study shows that, in addition to the influence of seasonal changes in the water masses, the distribution and composition of mesozooplankton are highly influenced by trophic interactions between zooplankton taxa, in the boundary waters of the Taiwan Strait and the East China Sea.     

Evidence of artisanal fishing impacts and depth refuge in assemblages of Fijian reef fish

Protection from fishing generally results in an increase in the abundance and biomass of species targeted by fisheries within marine reserve boundaries. Natural refuges such as depth may also protect such species, yet few studies in the Indo Pacific have investigated the effects of depth concomitant with marine reserves. We studied the effects of artisanal fishing and depth on reef fish assemblages in the Kubulau District of Vanua Levu Island, Fiji, using baited remote underwater stereo-video systems. Video samples were collected from shallow (5–8 m) and deep (25–30 m) sites inside and outside of a large old marine reserve (60.6 km², 13 years old) and a small new marine reserve (4.25 km², 4 years old). Species richness tended to be greater in the shallow waters of the large old reserve when compared to fished areas. In the deeper waters, species richness appeared to be comparable. The difference in shallow waters was driven by species targeted by fisheries, indicative of a depth refuge effect. In contrast, differences in the abundance composition of the fish assemblage existed between protected and fished areas for deep sites, but not shallow. Fish species targeted by local fisheries were 89% more abundant inside the large old reserve than surrounding fished areas, while non-targeted species were comparable. We observed no difference in the species richness or abundance of species targeted by fisheries inside and outside of the small new reserve. This study suggests that artisanal fishing impacts on the abundance and species richness of coral reef fish assemblages and effects of protection are more apparent with large reserves that have been established for a long period of time. Observed effects of protection also vary with depth, highlighting the importance of explicitly incorporating multiple depth strata in studies of marine reserves.     

A baited underwater video technique to assess shallow-water Mediterranean fish assemblages: Methodological evaluation

A baited underwater video (BUV) system for the study of reef-associated fish populations on shallow (10-20 m) rocky habitats in the western Mediterranean was assessed at four locations in Spain and two in France. We describe the apparatus and optimal deployment times for video sampling. Different species had different response times to the bait, with four response groups identified. Examination of species accumulation curves and fish abundance estimates over time revealed that a period of approximately 20 min deployment was sufficient to capture most species on video. The technique sampled a wide variety of species, with 51 species belonging to 33 families recorded. Nine species of fish appeared regularly at the bait in relatively high numbers, and consist of six carnivores (Serranus cabrilla, Serranus scriba, Coris julis, Diplodus annularis, Diplodus vulgaris, Thalassoma pavo), two planktivores (Chromis chromis, Boops boops) and one omnivore (Oblada melanura). However, abundance estimates for other species were generally very low (mean < 1 per location). Comparison of results from BUV with those obtained by Underwater Visual Census (UVC) at the same locations suggests that although BUV estimates species richness reliably, UVC is the more suitable technique for estimating the abundance of shallow-water reef fish in the Mediterranean. BUV improvements are suggested to optimise its use in deeper waters where UVC using scuba is inoperable.