北京河流大型底栖动物空间格局及其环境响应研究

大型底栖动物群落结构及多样性对于区域河流环境状况具有重要的指示意义。基于2014年5月—2015年8月间北京市河流大型底栖动物群落结构调查数据,分析底栖动物的生物多样性特征和空间格局。调查共发现大型底栖动物151种(或分类单元),隶属于5门9纲67科127属,水生昆虫占绝对优势。聚类分析表明76个采样点可被分为4组,组1主要包含北部山区的潮白河水系,具有较为典型的山溪型河流底栖动物特征,组2主要包含永定河山峡段和北运河水系的清河,组3主要包含大清河水系和北运河水系的温榆河、北沙河、南沙河等,二者具有城市河流兼有山溪型河流底栖动物的特征,组4主要包含北运河水系,具有典型的城市河流底栖动物特征。优势种分析表明:组1的优势种为热水四节蜉(Baetis thermicus)、秀丽白虾(Exopalaemon modestus)和网栖石蛾(Cheumatopsyche sp.),组2为直突摇蚊(Orthocladius sp.)、钩虾(Gammarus sp.)和长足摇蚊(Tanypus sp.),组3为摇蚊科幼虫(larvae of Chironomidae)和寡毛类(Oligochaeta),组4是以中华摇蚊(Chironomus sinicus)为代表的摇蚊幼虫。功能摄食类群研究表明:组1以收集者和滤食者占绝对优势,相对丰度分别为60%和29.6%;组2、组3、组4均以收集者占绝对优势,相对丰度分别为97.7%、90%、97.5%。物种数、Shannon-Wiener多样性指数、Pielou均匀度指数和Margalef丰富度指数的组间差异性显著(P0.05)。研究表明,北京河流大型底栖动物受河流自然环境变化的影响显著,形成了典型的山区-城市底栖动物空间格局,山区河流中保持了较高的生物多样性,城市河流及其过渡区的大型底栖动物退化明显,大型底栖动物能够明显指示环境状况的变化并可指导河流环境的保护与恢复。     

In situ respiration of benthic communities in Castle Harbor,Bermuda

In situ measurements of community respiration were made at two stations in Castle Harbor, Bermuda, during April and May, 1971. Total community respiration was 20.67 and 19.11 ml O₂ m^-2 h^-1 at Stations 1 and 2, respectively, in April. In May, respiration increased with water temperature to 26.99 and 24.56 ml O₂ m^-2 h^-1. Significant differences (P<0.05) existed between stations and sampling periods. Bacterial respiration was estimated from sediment treatment with streptomycin-SO₄. Values ranged from 7.71 to 8.72 ml O₂ m^-2 h^-1 in April and May, respectively. No significant difference existed between sampling periods or stations. No detectable chemical O₂ demand of the sediment, determined by a formalin treatment, was found. Total community respiration was further compartmentalized into macrofaunal, meiofaunal, and microfaunal-microfloral components. Both the macrofaunal and meiofaunal respiration was negligible compared to that estimated for the microfaunal-microfloral component.Contribution No. 2708 from the Woods Hole Oceanographic Institution, and Contribution No. 552 from the Bermuda Biology Station. This study was supported in part by National Science Foundation Grants GZ 1508 and GB 16161.     

鄱阳湖大型底栖动物群落结构的空间分布及影响因子研究

由于受人类活动干扰的加强以及受与长江干流之间"江湖关系"变化的影响,近年来鄱阳湖水生生态系统的状况及变化受到较多关注。对底栖动物群落结构的研究将有助于了解鄱阳湖生态系统结构现状及影响因子,对鄱阳湖保护对策的制定形成有效支撑。2016年7月,对鄱阳湖湖区(分别于鄱阳湖保护区和南矶山保护区)的底栖动物群落结构及相关环境因子进行了调查。调查共发现大型底栖动物27种,隶属于5门8纲,平均密度为48.40 ind.·m-2,其中主要以软体动物门为主;平均生物量为28.12 g·m-2,亦主要由软体动物门贡献。湖区主要优势种为河蚬(Corbicula fluminea)(优势度y=0.0655)、铜锈环棱螺(Bellamya aeruginosa)(y=0.0336)、霍甫水丝蚓(Limnodrilus hoffmeisteri)(y=0.0268)。底栖动物密度、生物量及多样性指数均呈现出鄱阳湖保护区高于南矶山保护区的格局,且二者在群落组成上有明显差异,鄱阳湖自然保护区主要以腹足纲和寡毛纲为主,南矶山自然保护区主要以瓣鳃纲和腹足纲为主。典范对应分析的结果显示,鄱阳湖保护区主要受到高水深、低浊度及高溶氧的影响;南矶山保护区各样点之间群落相似性较差,分别受不同因子的影响,这表明在各区域内部,局域微生境在局域群落结构的塑造上起主要作用,因此该区域内生态系统的保护应适当考虑空间尺度。     

Sedimentary Pigments and Organic Matter in Relation to Benthic Fauna in the Tan-Shui Estuary,Taiwan

The benthic ecological structure of the Tan-Shui estuary, Taiwan is changed due to long term effects of dumping of urban wastewater and of engineering actions. to monitor these changes, we sampled and analyzed benthos and sediment from 12 stations on the estuary.

The composition of the dominant species of benthos varied seasonally, with molluscan and crustacean species having greater numbers and higher frequencies of occurrence than other species. the dominant taxa during winter were Nassarius sp. and Maldanidae at two stations. Analysis using Simpson's index and Shannon's index showed the benthic community varied more in coastal areas than in offshore areas.

Physicochemical analysis showed that most of the Tan-Shui estuary consisted of sandy sediment. the variations in concentrations of organic carbon and total nitrogen at each station were small. Although the concentrations of chlorophyll-a and carotenoid at all stations were generally low, the two stations had the highest concentrations, and we concluded that the concentration of pigments in these sediments was related to the abundance of benthos. the community structure of the benthos reflected the characteristics of the sediments, and benthic species exhibited selection of and adaptation to specific sedimentary environments.     

Meiofauna densities and gastrotrich community composition in a Mediterranean sea cave

During the past 5 decades, the large-sized biota inhabiting dark marine caves has attracted the attention of many marine biologists; in contrast, studies concerning the meiofaunal organisms of these peculiar biotopes remain scanty and mostly with a taxonomic aim. In this study, the nature and abundance of meiofaunal taxa living in a Mediterranean, semi-submerged sea cave was surveyed in relation to distance from the entrance and over two different seasonal periods. Particular attention was paid to the Gastrotricha taxocene. Research was carried out in a cave along the Ionian coast of Apulia (southern Italy), the “Grotta Piccola del Ciolo” which opens for approximately 120 m on the north-eastern side of a shallow fjord and has a bottom blanketed by fine to very fine sand, occasionally rich in detritus. Quantitative samples in four replicates were collected by SCUBA diving, in November 2000 and June 2001, coring the sediment with a hand-held piston corer in three light-free sites (stations 1–3) located at increasing distances from the entrance. At each site, two additional 500-ml sediment samples were collected for an in vivo study of the Gastrotricha. Faunistic analysis found a fairly high meiobenthic diversity, identifying representatives of more than 12 major groups, with total abundances ranging from 656 ind./10 cm² (10 cm²) in November to 1,069 ind./10 cm² in June. Station 1, the closest to the entrance invariably hosted the most abundant meiofaunal community (851 ind./10 cm² in November and 1932 ind./10 cm² in June), followed by station 2 or 3 depending on the season. While nematodes and harpacticoids appear as the most abundant taxa when the cave is considered as a whole, other taxa may prevail numerically in selected stations, e.g. priapulids, which are the second most abundant taxon at station 1 (30 ind./10 cm² in November and 83 ind./10 cm² in June). Although the density of total meiofauna and that of the single groups may not be very high, the cave is interesting by virtue of the peculiarity of the hosted fauna, e.g., species and genera new to science or new to the Mediterranean Sea. Regarding the Gastrotricha, we found 16 species, accounting for 1.3–2.6% of the total meiobenthos (density = 8.4 ind./10 cm² in November and 27.4 ind./10 cm² in June). Analysis of the gastrotrich community found, particularly in June, an assemblage of taxa quite different from those found in open habitats, even at the family level; differences that are probably due to the exploitation of different food resources by animals populating the two environments, i.e. algae in the open sea versus bacteria in the caves. Results indicate that for meiofauna, as happens for macrofauna, the marine caves may represent hotspots of biodiversity and endemism; the driving forces at the base of the trophic depletion hypothesis seem to be responsible for structuring the meiofauna community inside the cave.     

Short-term patch dynamics of macroinvertebrate colonization on decaying reed detritus in a Mediterranean lagoon (Lake Alimini Grande,Apulia, SE Italy)

In aquatic ecosystems, the ecology of macrophytal detritus aggregations has been investigated over a range of temporal scales. Yet, no attempts have been made to minimize the temporal resolution of the analysis, thus neglecting the occurrence of short-term colonization and decay dynamics for these ephemeral patches of high biological activity. The present study was carried out at two sampling sites in Lake Alimini Grande, a brackish lagoon in South-East Italy. The abundance of macroinvertebrate taxa colonizing prepared packs of reed leaf detritus and the ash-free dry mass of the packs were monitored daily for 40 days. Spectral analysis was used to investigate the fine-scale temporal dynamics of invertebrates colonization and leaf pack mass variations. The macrobenthos found on leaf packs was dominated at both sites by few taxa (i.e., the vagile Lekanesphaera monodi, Microdeutopus gryllotalpa, Neanthes caudata and the sessile Balanus sp.), whose general colonization patterns were described by unimodal curves. At a daily temporal resolution Balanus sp. was characterized by random short-term density variations, while vagile taxa showed non-random, highly site- and species-specific fluctuations generally characterized by an oscillation period comprised between 2 and 3 days. In addition, leaf packs were characterized by non-random, short-term mass oscillations, coherent and in phase with L. monodi abundance fluctuations. Our results highlight the occurrence of short-term, non-random density variations of invertebrate colonizers on leaf detritus patches. In addition, they emphasize a previously unexplored, fine-scale linkage between abundance patterns of invertebrate consumers and short-term mass variations of decaying detritus.     

Tisbe (Copepoda: Harpacticoida) species from the Lagoon of Venice. I. Seasonal fluctuations and ecology

Distribution and abundance of Tisbe species were studied throughout a period of 3 years at 3 stations in the Lagoon of Venice (Italy). At 2 other stations samples were taken occasionally, as also at the Lido station (open sea). Twelve species may be considered as common inhabitants of the lagoon, and 3 species appear to be occasional transients, compared to the 9 species found at the Lido. A comparison of the physical data shows that the stations were similar in temperature and salinity, but differed primarily in pH values, sediment characteristics, algal substratum and faunal benthic community. The fact that remarkable differences in species composition and distribution of Tisbe could be observed between the various parts of the lagoon and the lagoon and the open sea, indicates that temperature and salinity are not so important for species diversity as are biotic factors. A particularly strong difference existed between samples taken at the bottom and from pilings, which constitute a very special biotope for the benthic communities in the lagoon and seem to be a preferred habitat for T. lagunaris and T. cucumariae. The data suggest that there is a certain interaction between T. holothuriae and the other species. Whenever T. holothuriae was abundant, the other species were rare, but T. clodiensis, T. dobzhanskii (Stations 1 and 2) and Tisbe sp. (Station 3) attained high relative abundance whenever T. holothuriae decreased considerably in number. T. holothuriae represents certainly the hardiest species of the lagoon, displaying a great ability to cope with stress conditions, even those present in the interior lagoon where strong fluctuations in salinity, temperature, pH and oxygen prevail.     

Impact of heavy metals of industrial plant wastewater on benthic communities of Bizerte Lagoon (Tunisia)

ABSTRACT

The aim of this study was to assess the consequences of human impact on the characteristics of sediments heavy metal concentration, grain size and its influence on the structure of the microbial and meiofaunal community assemblages. A survey was carried out in July 2013 within six sites located in the Bizerte Lagoon (Tunisia), both downstream and upstream of industrial effluents. The highest total sediment metal concentrations were detected in stations located close to the industrial sewage discharge points. In these stations, the lowest densities of the total meiofauna (33?±?13?ind/10?cm^?2) and conversely the highest densities of cultivable bacteria that are heavy metal resistant have been reported (16?±?80.34?CFU?g^?1). Univariate (ANOVA) and multivariate (MDS/CCA) analyses demonstrate high dissimilarity (0.06) in meiofaunal and bacterial community structures between downstream and upstream industrial sewages. Furthermore, canonical correspondence analysis CCA results indicated that heavy metal sediment contamination promoted bacteria that are resistant to heavy metals, while heterotrophic bacteria supported the development of meiofauna taxa. The results highlight the importance of bacteria/meiofauna interactions, as both meiofaunal and microbial communities give indications of the ecological impact of heavy metal contamination in sediment.     

Fine-scale distribution of juvenile cephalopods in the Scotia Sea and adaptive allometry of the brachial crown

The pelagic nekton community was sampled with the RMT 25 opening/closing net and a neuston net at two stations in the Scotia Sea south of the Antarctic Polar Front in the open ocean (Station 1) and on the South Georgia northwestern slope (Station 2). Downward oblique tows were made with the RMT 25 through discrete 200 m layers to 1000 m in daylight and darkness. A total of 119 cephalopods representing nine species were removed from the samples, and mantle and arm lengths were measured to the nearest 0.1 mm. The most abundant species at each station was an undescribed Brachioteuthis sp. (B. ?picta). Galiteuthis glacialis and Alluroteuthis antarcticus were caught at both stations. Histioteuthis eltaninae, Bathyteuthis abyssicola and Psychroteuthis glacialis were caught at Station 1. Mastigoteuthis psychrophila and a Chiroteuthis sp. were caught at Station 2. B. ?picta was present throughout the water column to 1000 m at both stations, with little evidence of ontogenetic descent. There was evidence for ontogenetic descent in G. glacialis. This species was absent from the Antarctic Surface Water (ASW) at Station 1, where it was concentrated in the Circumpolar Deep Water (CDW). At Station 2 it was present throughout the water column to 1000 m. The other species were all caught in the core of the CDW (>400 m). In juvenile B. ?picta, G. glacialis and A. antarcticus, growth of the brachial crown is positively allometric with respect to mantle length. Recent data on biomass spectra in high-latitude pelagic systems show that they are characterised by the presence of peaks of biomass separated by biomass minima. Positive allometric growth in the brachial crown of these antarctic oceanic squid is suggested to have evolved as an adaptation to the peaked, or domed, structure of the pelagic biomass spectrum which must be spanned by these predators as their optimum prey size increases with growth. Interspecific differences in the allometry of tentacle growth are probably related to differences in strategies for stalking and capture of prey.     

The possible association between selected sediment characteristics and the occurrence of benthic macroinvertebrates in a minimally affected river in South Africa

Forty-two families of which the vast majority associated with particles >2000?µm were found. Sediment particle sizes <2000?µm had a detrimental effect on biodiversity. The highest biodiversity was recorded at sites characterised by riffle and run habitats. Although relatively high concentrations of selected metals were present in the sediment, it was largely from geological origin and most probably not bioavailable. No significant correlation was demonstrated between variation in temperature, pH, and electrical conductivity and diversity and abundance of macroinvertebrates. Therefore, it can be concluded that, under these conditions, sediment particle size and biotope availability played a decisive role on the distribution and abundance of macroinvertebrate taxa.     

Zooplankton community structure and water flow in the lee of Helix Reef (Great Barrier Reef, Australia)

To investigate which physical processes contribute most in moulding zooplankton community structure in the waters close to coral reefs, light traps moored in a grid pattern were used to collect zooplankton from the sea surface at 16 stations on the downstream side of Helix Reef during three time periods (2100-2200, 2400-0100, and 0300-0400 hours) over three consecutive nights covering the new moon period in January 1992. Two distinct zooplankton communities were present: a community composed primarily of reef-resident, demersal plankton immediately to the south of the reef in an area of reduced flushing, and a community containing coastal and shelf-seas taxa at the more exposed sites in the open flow field. The fauna composition at a number of exposed stations was as rich as that at sheltered stations both in terms of number of taxa and diversity indices but was almost an order of magnitude less abundant. The reef-resident, demersal plankton community was dominated by gammarid amphipods, mysids, and polychaetes, whereas only transient, meroplanktonic forms such as echinoderm and echinopluteus larvae and shelf-seas, holoplanktonic forms such as doliolids and larvaceans were significantly more abundant in the exposed community. Zooplankton associations were apparently formed by a combination of hydrodynamic processes, spatial and temporal distribution patterns of individual taxa, specific behaviours of certain taxa, and the interactions among taxa at different trophic levels.     

The effects of catchment land use on water quality and macroinvertebrate assemblages in Otara Creek,New Zealand

The effect of catchment land use on water quality and macroinvertebrate communities was examined by using data gathered during a 2004 reconnaissance of nine sites in the Otara Creek, New Zealand. Data collected included macroinvertebrate, water chemistry and sediments characteristics. Macroinvertebrate data were used in metric and index calculations. A total of 61 macroinvertebrate taxa, with 3032 total individuals, were identified from the macroinvertebrates samples collected from nine sites in Otara Creek. The greatest number of macroinvertebrate taxa was recorded within bush sites (mean>25), while the urban sites had the least number of taxa (mean=10). Pasture sites were intermediate with the mean>17. Taxa number differed significantly across land use. Mean macroinvertebrates abundance varied across the sites and land uses. The highest macroinvertebrates mean abundance was recorded in urban and pasture sites, while bush sites had significantly lower mean abundance. Physico-chemical parameters decreased from bush toward urban streams. Biotic indices were sensitive to changes in macroinvertebrates community structure across land uses with mean scores decreasing from bush to urban and pasture streams. Ordination of biological data showed a clear separation of bush from urban and pastures streams. Analysis of similarities revealed significant differences in macroinvertebrates between both stream groups and land-use groups. The observed macroinvertebrate assemblage pattern was best correlated with a single variable, conductivity, temperature, turbidity, nitrate and dissolved oxygen. The combination of these environmental variables best explained the changes in the macroinvertebrate assemblages between sites. This study demonstrates that catchment land use may significantly affect the water quality and macroinvertebrate communities in an ecosystem.     

Seasonal succession and diversity of phytoplankton in a eutrophic lagoon (Liman lake)

The seasonal succession, composition and diversity of phytoplankton in a eutrophic lagoon (Liman lake) were studied between January 2002 and November 2003. Samples were collected from surface water and deeper (1 m depth) at stations and species diversity (Shannon-Weaver, H) and evenness were calculated. Shannon Diversty was similar at Station 1 and Station 2. Minimum and maximum diversity values (0.101 and 0.765 bits. mm3) were recorded in June and July 2003 at Station 2. Cluster analysis and NMDS (Non metric multidimensial scaling) were applied to the phytoplankton community. The lagoon exhibits high conductivity (7211-10757 microScm(-1)), mean temperature of 17.7 degrees C, varying concentrations of dissolved oxygen (3.3-8.4 mg l(-1)). Light, temperature, rainfall, turbidity and salinity were expected to be the main factors affecting the seasonal succession. The seasonal succession of phytoplankton were similar at surface water and 1 m depth. A total of 130 taxa belonging to Bacillariophyta, Chlorophyta, Euglenophyta, Cyanophyta, Dinophyta, Xantophyta, Chrysophyta and Cryptophyta divisions were identified. Pseudanabaena limnetica, Kirchneriella obesa, Kirchneriella lunaris, Ankistrodesmus falcatus and Ankistrodesmus spiralis were highly represented.     

江苏省不同营养状况湖泊底栖动物群落结构与多样性比较

为了解江苏省湖泊底栖动物群落结构和多样性并研究其对水环境质量变化的响应,于2012年春秋两季对江苏省16个湖泊51个采样点湖泊底栖动物群落结构与多样性以及湖泊综合营养状态指数进行调查,分析水质指标与底栖动物指数间Pearson相关关系。结果表明,江苏省16个湖泊营养状态指数范围为35.5~66.4,其中约81.2%的湖泊处于轻度-中度富营养状态,表明水质从好到中度污染;湖泊底栖动物优势种为寡毛类的霍甫水丝蚓(Limnodrilus hoffmeisteri),优势度为13.0%;香浓多样性指数(Shannon-Wiener diversity index)范围为0.00~2.20,级别范围由极贫乏到较丰富状态,表明水质污染程度从重度到轻度污染。从全省尺度看,水质评价结果与生物学(香浓多样性指数、Pielou均匀度指数和Biotic Index(BI)指数)评价结果存在一定差异。与历史数据相比,江苏省湖泊底栖动物清洁敏感物种减少甚至消失,总体群落结构趋于小型化。16个湖泊水体总氮和总磷与底栖动物密度呈显著负相关,而综合营养状态指数与底栖动物指数(香浓多样性指数、Pielou均匀度指数和BI指数)间关系不显著。上述研究结果表明综合营养状态指数无法完全客观反映湖泊水生态健康状况,因此需要综合水质、水文、水生生物、生境状况等因素发展新的评价指标体系。     

Effects of ocean acidification on invertebrate settlement at volcanic CO2 vents

We present the first study of the effects of ocean acidification on settlement of benthic invertebrates and microfauna. Artificial collectors were placed for 1 month along pH gradients at CO₂ vents off Ischia (Tyrrhenian Sea, Italy). Seventy-nine taxa were identified from six main taxonomic groups (foraminiferans, nematodes, polychaetes, molluscs, crustaceans and chaetognaths). Calcareous foraminiferans, serpulid polychaetes, gastropods and bivalves showed highly significant reductions in recruitment to the collectors as pCO₂ rose from normal (336–341 ppm, pH 8.09–8.15) to high levels (886–5,148 ppm) causing acidified conditions near the vents (pH 7.08–7.79). Only the syllid polychaete Syllis prolifera had higher abundances at the most acidified station, although a wide range of polychaetes and small crustaceans was able to settle and survive under these conditions. A few taxa (Amphiglena mediterranea, Leptochelia dubia, Caprella acanthifera) were particularly abundant at stations acidified by intermediate amounts of CO₂ (pH 7.41–7.99). These results show that increased levels of CO₂ can profoundly affect the settlement of a wide range of benthic organisms.     

Photographic and acoustic tracking observations of the behaviour of the grenadier Coryphaenoides (Nematonurus) armatus the eel Synaphobranchus bathybius,and other abyssal demersal fish in the North Atlantic Ocean

Using an autonomous free-fall vehicle (AU-DOS), observations were made of demersal fish attracted to baits and baited acoustic transmitters at two stations in the North Atlantic Ocean. A comparison was made between Station PAP (48°50N; 16°30W), 4800 m deep on the Porcupine Abyssal Plain which is relatively eutrophic, and Station MAP (31°N; 20°W), 4900 m deep on the Madeira Abyssal Plain, which is oligotrophic. Experiments were conducted during summer, in 1989 and 1990. Four species of fish were observed at Station MAP, the grenadier, Coryphaenoides (Nematonurus) armatus, the eel, Synaphobranchus bathybius, and the ophidiids Spectrunculus grandis, and Barathrites sp. At Station PAP, C. (N.) armatus and H. (S.) bathybius were attracted to bait on all deployments and only two other individuals of different species, probably ophidiids, were seen. The mean first grenadier arrival time was 30 and 138 min at Stations PAP and MAP, respectively. Mean first eel arrival time was 29 and 151 min at Stations PAP and MAP, respectively. Estimated population densities of fish were 167 grenadiers km^-2 and 180 synaphobranchid eels km^-2 at Station PAP and 8 grenadiers km^-2 and 7 eels km^-2 at Station MAP. Only the grenadier C. (N.) armatus definitely ingested transmitters, and this species dominated fish activity around the baits. Mean time of departure of grenadiers with transmitters in their stomachs across an acoustic horizon at 1000 m range was 371 and 488 min at Stations PAP and MAP, respectively. Grenadiers had a longer mean staying time at the food source at the more oligotrophic Station MAP (364 min) than at Station PAP (141 min). This corresponds with predictions of optimal foraging theory.     

Benthic community respiration in the N.W. Atlantic Ocean: in situ measurements from 40 to 5200 m

Benthic community respiration was measured in situ at 9 stations along the Gay Head-Bermuda transect from depths of 40 to 5200 m. Three methods were used; bell jar respirometers, grab respirometers, and free vehicle respirometers. Benthic community respiration rates spanned three orders of magnitude, decreasing from 21.5 ml O₂ m^-2 h^-1 at 40 m in November to 0.02 ml O₂ m^-2 h^-1 at 5200 m. Rates decreased two orders of magnitude between 40 and 1800 m and then significantly declined again between the continental rise (3650 m) and the abyssal plain stations. Predictive equations for benthic community respiration along the transect reflect a strong correlation with depth of water. Of lesser significance are the correlations with water temperature, dissolved oxygen, benthic animal biomass, surface primary productivity and sediment organic matter. Calculations show that annual benthic respiration can utilize 1 to 2% of the surface primary productivity. Of the 2 to 7% organic carbon fixed at the surface which supposedly reaches the bottom, only 15 to 29% is utilized by the benthic community at 2200, 3000, and 3650 m. The energy requirements of other biological components of deep-sea benthic communities, such as benthopelagic and macro-epibenthic animals, not included in these measurements, must also be considered in calculating a balance of carbon.Contribution from Scripps Institution of Oceanography.     

Cross-shelf distribution of copepods and fish larvae across the central Great Barrier Reef

The distribution of total dry weight of zooplankton, copepod numbers and ichthyoplankton across the outer continental shelf in the central Great Barrier Reef was examined at bi-weekly intervals for three months over summer of 1983. Copepods were sampled (236 m net) within 10 m of the surface and within 10 m of the bottom. Mean densities in surface waters decreased markedly from the mid-shelf to outer shelf and the Coral Sea, but no cross-shelf gradient occurred in the bottom-water. Densities of copepods on the mid-shelf (surface and bottom waters) and in bottom-waters of the outer shelf were typically ca. 400 m^–3. Significantly lower densities (ca. 100 m^–3) occurred in surface waters of the outer shelf, except during outbursts of Acartia australis, when densities in these waters differed little from those elsewhere on the shelf. In oceanic waters, 10 km from the outer shelf station, copepod densities in surface waters were ca. 40 m^–3. Four of the five most abundant copepod taxa in surface waters, Paracalanus spp., Eucalanus crassus, Acrocalanus gracilis and Canthocalanus pauper, tended to be most abundant at the mid-shelf end of the transect. Acartia australis was sporadically very abundant in surface waters of the outer shelf, as was Paracalanus spp. in bottom-water of the outer shelf. An assemblage of Coral Sea species of copepod occurred in bottom-water of the outer shelf during two major intrusions, but not at other times. Densities of all common species varied considerably between cruises. Maximum densities of all common species except A. australis tended to be associated with diatom blooms linked to intrusions but a bloom did not necessarily mean all common species were abundant. Fish larvae included both reef and non-reef taxa, with reef taxa predominating on the outer shelf (approx 2:1 in density of individuals) and non-reef taxa dominating in nearshore samples (approx 2:1). Nine of the ten most abundant taxa analysed showed highly significant variation in numbers among stations and all but one of these also exhibited significant station x cruise interactions. Interactions generally reflected changes in the rank importance of adjacent stations from one cruise to the next or lack of any significant cross-shelf variation on some cruises where overall abundance of the taxa was low.     

Planktonic bioluminescence in the pack ice and the marginal ice zone of the Beaufort Sea

An icebreaker cruise into the Beaufort Sea in the fall of 1986 provided a unique opportunity for studying planktonic bioluminescence in ice fields and in the marginal ice zone. Bathyphotometer casts (bioluminescence intensity, seawater temperature, beam attenuation coefficient, and salinity) and biological collections were made to a depth of 100 m. A light budget, which describes the planktonic species responsible for the measured bioluminescence, and a dinoflagellate species budget were constructed from the mean light output from luminescent plankton and plankton counts. The vertical distribution of bioluminescence among the ice stations was similar. The maximum intensities were 2 to 8×10⁶ photons s^-1 cm^-3 in the upper 50 m of the sea-ice interface. The marginal ice zone station (MIZ) exhibited a maximum intensity of 2 to 3×10⁸ photons s^-1 cm^-3 between 5 and 30 m depth. At Ice Station 2, Metridia longa and their nauplii contributed approximately 80% of stimulable bioluminescence in the upper 10 m but, overall, Protoperidinium spp. dinoflagellates contributed most of the light to a depth of 100 m. In the MIZ, Protoperidinium spp. dinoflagellates contributed 90% of the light within the upper 10 m, decreasing to 43% of the contributed light at a depth of 40 m. Below 40 m, dinoflagellate bioluminescence decreased to a few percent of the total to a depth of 90 m. Metridia spp. copepods contributed more than 50% of the light at depths from 40 to 90 m. Ostracods, larvaceans, and euphausiid furcilia contributed <1% of all bioluminescence at all depths sampled. Correlation analyses between measured bioluminescence (photons s^-1 cm^-3), the number of bioluminescent dinoflagellates and the light budget for the MIZ indicated highly significant associations: r=0.919, p=0.001, and r=0.912, p<0.001, respectively (Student's two-tailed t-tests). Bioluminescence was negatively correlated with seawater salinity at all stations (p=0.001). Maximum bioluminescence was measured in the less saline surface waters at all stations.     

Sewage nutrient enrichment and phytoplankton ecology along the central coast of Lebanon

The abundance and taxonomic diversity of phytoplankton has been studied in relation to sewage pollution (proximity to outfalls) south of Beirut, Lebanon. Surface-water samples were collected from a series of beach stations extending from the American University of Beirut to 20 km south from June, 1973 to July, 1974. Samples were preserved, concentrated by settling, and the concentration of each taxon of phytoplankton enumerated in an inverted microscope. Water samples from the vicinity of two major sewer outfalls (Carlton and Khalde sewers) showed very high concentrations of NH₄ ⁺, NO₂ ^-, NO₃ ^- and PO₄ ^-3, a greater total concentration of phytoplankton, and a lower taxonomic diversity than samples remote from outfalls. A considerable variation in the occurrence of species and dominance occurred along the pollution gradient. Blue-green algae and dinoflagellates were dominant in polluted waters, while diatoms dominated in cleaner water away from major sewage outflow. From the dominance and relative distribution of the taxa along the pollution gradient, certain taxa (Oscillatoria spp., Spirulina spp., Phormidium spp., Synochococcus custos and S. elongatus, Gymnodinium spp., and Prorocentrum spp.) emerge as indicator species of pollution. These changes correspond to a typical degradation of a complex community to a less mature state by the inflow of nutrient-rich sewage (eutrophication) along a coastal region about 10 km long.