Distribution of gravel-sized empty tests of large benthic foraminifers as practical depositional indicators in tropical reef and shelf carbonate environments

To explore the utility of gravel-sized tests of large benthic foraminifers (LBFs) as practical paleoenvironmental indicators of tropical reef and shelf carbonate environments, depth and spatial distributions of gravel-sized empty tests of LBFs were examined using 39 surface sediment samples collected from depths shallower than 200 m off the west coast of Miyako Island (Ryukyu Islands, northwest Pacific). Distributions of the LBF tests were mainly related to water depth, topography, and substrate type. Q-mode cluster analysis based on the binary (presence/absence) data of LBF associations (4–2-mm size fraction) clearly delineates four depositional environments: bay, back reef to fore reef, flat shelf, and shelf slope. Application of this modern dataset to fossil LBF data from larger foraminiferal limestones of the Pleistocene Ryukyu Group indicate that a test section was deposited in an outer flat shelf at depths between 54 and 99 m. Comparisons of these results with previous reports suggest that our foraminiferal analysis using gravel-sized tests is methodologically easier than conventional analyses including smaller sized tests to distinguish similar levels of depositional environments. However, taxonomic and environmental similarities make the applicability of this dataset to fossil LBF data from Quaternary tropical carbonate environments in the northwest Pacific.     

Effects of thermal history on the responses to thermal stress of a large benthic foraminifera,Calcarina gaudichaudii

Marine ecosystems, particularly coastal environments, are rapidly changing due to anthropogenic impacts resulting in increased global climate change (ocean warming), ocean acidification, hypoxia, and eutrophication. On coral reefs, symbiont-bearing large benthic foraminifera (LBFs) can play a key role as reef constituents and carbonate producers, contributing up to 5% of reef-scale carbonate budgets. However, projected climate change, particularly ocean warming, has the potential to significantly alter the conditions in which marine organisms persist. While the response of LBFs to elevated thermal stress is well documented in laboratory studies, the potential influence of adaptation or acclimatization through prior environmental thermal history on this response remains largely unknown. In this study, specimens of Calcarina gaudichaudii, an LBF from the Penghu Islands, Taiwan, were collected from thermally variable intertidal and thermally stable subtidal (~ 6 m depth) environments representing thermal history. LBFs were then acclimated to laboratory conditions at ambient (25 °C) and elevated (28 °C) temperatures for three weeks, and subsequently exposed to control and heat stress treatments (25 °C, 28 °C, 30 °C, 33 °C) for an additional one week. Photosynthetic rates (determined through oxygen flux measurements) of C. gaudichaudii significantly decreased in specimens collected at subtidal depths acclimated at 25 °C when compared to those acclimated at 28 °C, whereas there was no effect of thermal history on respiration, indicating that symbiont and holobiont responses may differ in LBFs. Additionally, maximum photochemical efficiency (Fv/Fm) significantly decreased as a result of heat stress, although bleaching was not visually observed after one week. These results highlight the plastic responses of the algal microbiome and indicate that thermal history, acclimatization temperature, and heat stress interact to affect the physiological status of C. gaudichaudii. This study adds to the growing literature which highlights the larger implications of understanding thermal history as an important factor to consider to better understand how ecosystem processes (e.g., carbonate production) are altered on modern coral reefs.

     

Is increased calcarinid (foraminifera) abundance indicating a larger role for macro-algae in Indonesian Plio-Pleistocene coral reefs?

An important question in coral reef ecology is whether algal abundance in coral reef eco-systems is a natural phenomenon, or has increased as a result of coral reef degradation ultimately resulting in coral–algal regime shifts. Regime shifts, from coral to macro-algae dominated, alter the three-dimensional habitat structure in coral reef ecosystems. Surprisingly, few studies have looked at the effects for species that inhabit the reefs without being the architects of the three-dimensional structure. In this study the effects of a change in habitat characteristics on the community structure of large benthic foraminifera (LBF) is compared between an area with high (Kepulauan Seribu) and lower (Spermonde Archipelago) anthropogenic influence. The results indicate a general relationship between habitat and LBF assemblage structure. The largest difference was observed in shallow habitats. Habitats dominated by algae are inhabited by a specific group of LBF, the Calcarinidae, and domination of this group increases with higher algal prevalence. The fossil record of this group indicates that they evolved following a major change in settings of the central Indo-West-Pacific coral reefs from land detached platforms to fringing reefs, about 5 million years ago. Understanding the biotic response to this transition in reef morphology and the associated increase in terrestrially derived nutrients forms an excellent challenge to gain insights in present-day threats to coral reef ecosystems.     

Distribution and sediment production of large benthic foraminifers on reef flats of the Majuro Atoll,Marshall Islands

The distributions and population densities of large benthic foraminifers (LBFs) were investigated on reef flats of the Majuro Atoll, Marshall Islands. Annual sediment production by foraminifers was estimated based on population density data. Predominant LBFs were Calcarina and Amphistegina, and the population densities of these foraminifers varied with location and substratum type on reef flats. Both foraminifers primarily attached to macrophytes, particularly turf-forming algae, and were most abundant on an ocean reef flat (ORF) and in an inter-island channel near windward, sparsely populated islands. Calcarina density was higher on windward compared to leeward sides of ORFs, whereas Amphistegina density was similar on both sides of ORFs. These foraminifers were more common on the ocean side relative to the lagoon side of reef flats around a windward reef island, and both were rare or absent in nearshore zones around reef islands and on an ORF near windward, densely populated islands. Foraminiferal production rates varied with the degree to which habitats were subject to water motion and human influences. Highly productive sites (>10³ g CaCO₃ m⁻² year⁻¹) included an ORF and an inter-island channel near windward, sparsely populated islands, and a seaward area of a reef flat with no reef islands. Low-productivity sites (<10 g CaCO₃ m⁻² year⁻¹) included generally nearshore zones of lagoonal reef flats, leeward ORFs, and a windward ORF near densely populated islands. These results suggest that the distribution and production of LBFs were largely influenced by a combination of natural environmental factors, including water motion, water depth, elevation relative to the lowest tidal level at spring tide, and the distribution of suitable substratum. The presence of reef islands may limit the distribution and production of foraminifers by altering water circulation in nearshore environments. Furthermore, increased anthropogenic factors (population and activities) may adversely affect foraminiferal distribution and production.     

Seasonally changing habitat use patterns among roving herbivorous fishes in the southern Red Sea: the role of temperature and algal community structure

Coral reefs are characterized by intense herbivory. Spatial patterns in herbivory—particularly along the depth gradient—influence the distribution and abundance of algae. Depth gradients in herbivorous reef fishes are generally assumed to be temporally stable, but this assumption has rarely been questioned. Here, we use underwater visual census and herbivore exclusion experiments to study the community composition and temporal patterns in habitat use by roving herbivorous fishes in an environment characterized by profound seasonal changes in algal biomass and distribution and extreme summer temperatures. Among the 18 species of roving herbivores recorded, parrotfishes were dominant in species richness and biomass, while regional endemic species represented 77 % of the total biomass. During most of the year, roving herbivores aggregate in the shallow reef zones and their biomass declines with depth. The herbivore community on the reef flat is distinct from that in deeper zones. The former is characterized by Siganus rivulatus, Acanthurus gahhm and Hipposcarus harid, while the deeper reef zones are characterized by S. ferrugineus, Chlorurus sordidus and Ctenochaetus striatus. In summer, the distinct community structures among reef zones are lost as reef flat herbivores tend to exploit deeper reef zones and some reef crest species venture on to the reef flat. This summer change in herbivore distribution is also reflected in reduced turf biomass and increased yield to herbivores in the deeper reef zones. Habitat use is related to the feeding mode such that browsers dominate the reef flat and scrapers the reef crest, while the seasonal changes correspond to changes in availability of targeted algal resources. These seasonal changes appear to be driven by the extreme temperatures in summer, reaching 36 °C on the shallow reef flat.     

Grazer biomass correlates more strongly with production than with biomass of algal turfs on a coral reef

The biomass of large herbivorous grazing fish on the shallow reef crest of Myrmidon Reef, Great Barrier Reef, is 7.0 times that on the reef slope (15 m depth), and 2.3 times that on the reef flat. Biomass of algal turfs on the crest was only 1.4 and 1.0 times that on the slope and flat, respectively. In contrast, rate of production of algal turfs on the crest was 5.3 and 2.8 times that on the slope and flat, respectively. A multiple correlation between large grazer biomass, algal turf biomass, and algal turf production across the three zones showed that only rate of algal production correlated significantly with large grazer biomass (algal production p=0.007, algal biomass p=0.418). This result suggests that large grazers may aggregate in zones of highest algal turf production. The mechanisms by which fish respond to habitat-specific differences in food production remain unclear.     

新疆塔什库尔干野生动物自然保护区马可波罗盘羊生境适宜性评价

马可波罗盘羊是帕米尔高原的代表性物种,开展生境适宜性评价对于该物种的保护与管理具有重要意义。综合考虑植被、地形等影响马可波罗盘羊生境选择的关键因子,以及道路和牧场等人为干扰因子,借助ArcGIS,构建生境适宜性指数模型,在不同尺度上评价分析马可波罗盘羊的生境适宜性及其季节变化特征。结果表明:15836 km~2保护区内马可波罗盘羊夏季潜在适宜生境面积为2127.19 km~2,冬季为1915.70 km~2。保护区西北部面积3767.73 km~2的马可波罗盘羊实际分布区内,夏季潜在适宜生境面积为1095.48 km~2,冬季为1072.82 km~2,马可波罗盘羊适宜生境集中分布于保护区内该物种实际分布区。受人为干扰,保护区内马可波罗盘羊夏季和冬季实际适宜生境丧失率分别为18.43%和17.78%,实际分布区内适宜生境丧失率分别为33.65%和29.73%,表明实际分布区马可波罗盘羊适宜生境受人类活动影响较大,应予以重点保护。总体而言,影响马可波罗盘羊生境适宜性的关键因素是国道314和放牧。基于上述研究结果,作者提出了4点关于马可波罗盘羊生境保护,以及保护区管理与规划的建议与思考。     

Pan‐Arctic sea ice‐algal chl a biomass and suitable habitat are largely underestimated for multiyear ice

There is mounting evidence that multiyear ice (MYI) is a unique component of the Arctic Ocean and may play a more important ecological role than previously assumed. This study improves our understanding of the potential of MYI as a suitable habitat for sea ice algae on a pan‐Arctic scale. We sampled sea ice cores from MYI and first‐year sea ice (FYI) within the Lincoln Sea during four consecutive spring seasons. This included four MYI hummocks with a mean chl a biomass of 2.0 mg/m², a value significantly higher than FYI and MYI refrozen ponds. Our results support the hypothesis that MYI hummocks can host substantial ice‐algal biomass and represent a reliable ice‐algal habitat due to the (quasi‐) permanent low‐snow surface of these features. We identified an ice‐algal habitat threshold value for calculated light transmittance of 0.014%. Ice classes and coverage of suitable ice‐algal habitat were determined from snow and ice surveys. These ice classes and associated coverage of suitable habitat were applied to pan‐Arctic CryoSat‐2 snow and ice thickness data products. This habitat classification accounted for the variability of the snow and ice properties and showed an areal coverage of suitable ice‐algal habitat within the MYI‐covered region of 0.54 million km² (8.5% of total ice area). This is 27 times greater than the areal coverage of 0.02 million km² (0.3% of total ice area) determined using the conventional block‐model classification, which assigns single‐parameter values to each grid cell and does not account for subgrid cell variability. This emphasizes the importance of accounting for variable snow and ice conditions in all sea ice studies. Furthermore, our results indicate the loss of MYI will also mean the loss of reliable ice‐algal habitat during spring when food is sparse and many organisms depend on ice‐algae.     

Effects of extreme seasonality on community structure and functional group dynamics of coral reef algae in the southern Red Sea (Eritrea)

Spatial and temporal variation in the biomass of four functional groups of coral reef algae (canopy algae, foliose algae, turf algae and crustose corallines) was investigated in the southern Red Sea. This region is characterised by extremely high summer temperatures (ca. 35°C). Strong seasonal shifts in the relative contribution of each group to the total macroalgal biomass were observed. On the reef flat, canopy and foliose algae dominated in winter, retaining low biomass in summer. On the fore reef, crustose corallines accounted for most of the macroalgal biomass throughout the year. Turf algae contributed least to the total biomass in all reef zones; biomass peaks shifted from midsummer on the inner reef flat to winter in the deeper zones. Biomass correlated negatively with seawater temperature in most groups, but the correlation was positive for turf algae on the shallow reef flat. We hypothesise both direct and indirect effects of the strong seasonality.

Prey and tigers on the forgotten trail: high prey occupancy and tiger habitat use reveal the importance of the understudied Churia habitat of Nepal

Tigers are globally threatened and their conservation relies on intact habitat that supports key large prey. The Churia habitat is relatively unknown even though it occupies a significant portion of the forested landscape of the Terai Arc, which stretches over 1000 km in a narrow band across Nepal and India, parallel to the Himalayas. To address this lack of detailed information relevant to tiger conservation, we used sign surveys to estimate occupancy probability for 5 focal prey species of tigers (gaur, sambar, chital, wild pig, and barking deer), and assess tiger habitat use within 537 km² of the understudied Churia habitat in Chitwan National Park (CNP), Nepal. Multi-season occupancy models allowed us to make seasonal (winter vs. summer) inferences regarding changes in occupancy or habitat use based on covariates influencing occupancy and detection. We found that sambar had the largest spatial distribution occupying 431–437 km², while chital had the smallest at 100–158 km² across both seasons. The gaur population showed the most seasonal variation occupying from 413 to 318 km², suggesting their migration out of the Churia in summer and moving in during winter. Wild pigs showed the opposite trend occupying from 444 to 383 km²; suggesting moving into Churia in summer and out in winter. Barking deer were widespread in both seasons (329–349 km²). Tiger habitat use (\({{\hat{\varPsi } }}({\text{SE}})\)) was higher in winter 0.63 (0.11) than in summer 0.54 (0.21), but confidence intervals overlapped and area used was similar across seasons, 337 km² (winter) to 291 km² (summer). Available habitat, distribution of water sources, and human disturbance were the most common variables influencing spatial distribution of prey and habitat use of tigers at different spatial scales. Overall, we found high prey occupancy and tiger habitat use, suggesting the Churia is valuable habitat for ungulates and tigers. Given that this habitat accounts for 639 km² within CNP and 7642 km² across the entire Terai Arc, the Churia should no longer be neglected in global tiger conservation planning.     

Effects of Seasonal Folivory and Frugivory on Ranging Patterns in <Emphasis Type="Italic">Rhinopithecus roxellana</Emphasis>

The distribution of food resources in time and space may affect the diet, ranging pattern, and social organization of primates. We studied variation in ranging patterns in a group of Sichuan snub-nosed monkeys (Rhinopithecus roxellana) over winter and summer in response to variation in their diet in the Qingmuchuan Nature Reserve, China. There was a clear diet shift from highly folivorous in winter to highly frugivorous in summer. The home range was 8.09 km² in summer and 7.43 km² in winter, calculated via the 95% kernel method. Corresponding to the diet shift, the focal group traveled significantly longer distances in summer (mean 1020 ± 69 m/d) than in winter (mean 676 ± 53 m/d); the daily range was also significantly greater in summer (mean 0.27 ± 0.02 km²/d) than in winter (mean 0.21 ± 0.01 km²/d). There was no significant variation in home range size between winter and summer, and the monkeys did not use geographically distinct ranges in summer and winter. However, overlap in the actual activity area and core range between winter and summer was only 0.13 km², representing 4.4% of the summer core area and 5.3% of the winter core area. Differences were apparent between summer and winter ranging patterns: In summer, the group traveled repeatedly and uninterruptedly across its home range and made 3 circles of movement along a fixed route in 31 d; in winter, the activity area was composed of 3 disconnected patches, and the focal group stayed in each patch for an average of 8 successive days without traveling among patches. Winter range use was concentrated on mixed evergreen and deciduous forest patches where leaves and fruits were available, whereas the summer range pattern correlates significantly positively with the distribution of giant dogwood (Cornus controversa) fruits. Thus it appears that the diet shift of Sichuan snub-nosed monkeys between winter and summer caused the monkeys to use their home range in different ways, supporting the hypothesis that food resources determine primate ranging patterns.     

The role of the reef flat in coral reef trophodynamics: Past,present, and future

The reef flat is one of the largest and most distinctive habitats on coral reefs, yet its role in reef trophodynamics is poorly understood. Evolutionary evidence suggests that reef flat colonization by grazing fishes was a major innovation that permitted the exploitation of new space and trophic resources. However, the reef flat is hydrodynamically challenging, subject to high predation risks and covered with sediments that inhibit feeding by grazers. To explore these opposing influences, we examine the Great Barrier Reef (GBR) as a model system. We focus on grazing herbivores that directly access algal primary productivity in the epilithic algal matrix (EAM). By assessing abundance, biomass, and potential fish productivity, we explore the potential of the reef flat to support key ecosystem processes and its ability to maintain fisheries yields. On the GBR, the reef flat is, by far, the most important habitat for turf‐grazing fishes, supporting an estimated 79% of individuals and 58% of the total biomass of grazing surgeonfishes, parrotfishes, and rabbitfishes. Approximately 59% of all (reef‐wide) turf algal productivity is removed by reef flat grazers. The flat also supports approximately 75% of all grazer biomass growth. Our results highlight the evolutionary and ecological benefits of occupying shallow‐water habitats (permitting a ninefold population increase). The acquisition of key locomotor and feeding traits has enabled fishes to access the trophic benefits of the reef flat, outweighing the costs imposed by water movement, predation, and sediments. Benthic assemblages on reefs in the future may increasingly resemble those seen on reef flats today, with low coral cover, limited topographic complexity, and extensive EAM. Reef flat grazing fishes may therefore play an increasingly important role in key ecosystem processes and in sustaining future fisheries yields.     

Trophic significance of herbivorous macroinvertebrates on the central Great Barrier Reef

The common herbivorous macroinvertebrates on reef flats of the central Great Barrier Reef (GBR) were, in order of abundance: gastropod molluscs (Turbo and Trochus spp.); pagurid crabs; and the starfish, Linckia laevigata. The density of macroinvertebrates on Davies Reef was lowest in the thick-turf habitats at the windward reef-crest (0.6–0.9 m^–2) compared with 3.1 to 5.2 m^–2 elsewhere on the reef flat. Invertebrate grazer densities were similar on mid-shelf reef flats (mean: 2.3–3.6 m^–2) and significantly lower on outer-shelf reefs (0.3–1.0 m^–2). The ingestion rate of Turbo chrysostomus, the most abundant macroinvertebrate species, was derived from (a) faecal production and food absorption efficiency, (b) comparison of algal biomass on grazed and ungrazed natural substrata and (c) gut-filling rate and feeding periodicity in field populations. The ingestion rate of Trochus pyramis, the most common trochid and an abundant component of the macroinvertebrate fauna, was also estimated using (a). This gastropod fed continuously, whereas T. chrysostomus showed a distinct nocturnal feeding periodicity. T. chrysostomus and T. pyramis ingested daily means of 35 and 54 mgC animal^-1, respectively. Total gastropod grazing rates (mgC m^–2d^-1 in the field ranged from 11 in a thick-turf, reef-crest habitat to 144 on the open-grazed main flat. Grazing by gastropods accounted for between 0.3 and 8% of the net production of benthic algal food resources, depending on location on the reef flat. Across the whole reef flat the mean (areally-weighted) gastropod grazing rate was 6% of net production. A comparison of the relative roles of different types of grazers led to the conclusion that fishes are likely to have the greatest overall trophic impact on reefs of the central GBR. Even where macroinvertebrates are most abundant on reef flats, the yield from benthic algal communities to macroinvertebrates is estimated to be only one third of that due to fishes.Contribution no. 471 from the Australian Institute of Marine Science     

中街山列岛海洋保护区鱼类物种多样性

基于2010-2012年在中街山列岛海洋保护区进行的8个航次底拖网调查数据资料,从鱼类分类学和生态类群等方面,结合多样性、资源密度和相对重要性指数,对该保护区鱼类物种多样性特征进行了分析。调查海域共采集鱼类55种,隶属2纲12目32科44属。其中,鲈形目鱼类26种,占47.3%;趋礁性鱼类41种,占74.5%;暖温性、暖水性和冷温性鱼类分别为30、24和1种,其中暖水种约占所有偶见种的70%;定居种、近海洄游种和季节性种分别为27、24和24种;底层、近底层和中上层鱼类分别占40.0%、36.4%和23.6%,其中矛尾鰕虎鱼(Chaeturichthys stigmatias)、龙头鱼(Harpodon nehereus)和鳀科鱼类分别成为各水层的绝对优势种。所有调查站点鱼类平均生物量指数夏季最高(1043.7 kg/km²),春季最低;尾数密度指数春季最高(122×10³ 尾/km²),冬季最低;生物量与尾数密度指数最高与最低季节之间均存在显著性差异(P<0.05)。对多样性的分析显示,Margalef丰富度(D)冬季最高,秋季最低,Shannon-Wiener多样性(H')与Pielou均匀度(J')均为夏季最高,秋季最低。聚类和NMDS方法分析显示不同季节鱼类群落组成格局差异极显著(P<0.01)。研究结果表明,中街山列岛海洋保护区鱼类资源结构受近海季节性洄游种类影响较大,鱼类分布季节动态多呈现洄游性更替节律,保护区内虽已出现鱼类多样性下降趋势和生态系统功能退化现象,传统经济种类的优越性在逐渐下降或边缘化,但独特的岛礁生境仍能很好地发挥着维持固有种类和提供良好栖息场所的优势,随着海洋牧场建设与一系列资源保护与修复措施,石首鱼科幼体已形成优势群体,而且保护区内出现大量小型饵料鱼类。     

唐家河国家级自然保护区川金丝猴生境适宜性评价

生境适宜性评价是濒危物种保护的重要基础。川金丝猴（Rhinopithecus roxellana）是栖息于温带森林的、中国特有的珍稀灵长类动物。位于岷山山系的四川唐家河国家级自然保护区是川金丝猴的重要分布地之一,但涉及该地区川金丝猴的生境信息却较缺乏。运用最大熵（Maximum entropy,MaxEnt）模型对四川唐家河国家级自然保护区川金丝猴不同季节的生境适宜性进行了研究,发现四个季节的训练集和验证集的受试者工作特征曲线下面积（Area under the receiver operator characteristic curve,AUC）值均超过0.8,说明模型预测结果较好。结果显示：（1）影响不同季节川金丝猴分布的主要因子是海拔、河流和道路。（2）川金丝猴的适宜生境面积存在季节性变化。其中,春季的适宜生境面积最大,为233.94 km²,占全区面积的58.48%;夏季的次之,为192.75 km²,占48.19%;秋冬季的适宜生境面积相对较低,分别为145.54 km²（占36.39%）和142.63 km²（占35.66%）。（3）川金丝猴的适宜生境分布具有明显的季节性垂直变化。研究揭示保护好完整的森林植被带对川金丝猴的生存具有重要意义,尤其要重视对人为干扰较强的低海拔生境的保护。     

Dissolved inorganic carbon and total alkalinity of a Hawaiian fringing reef: chemical techniques for monitoring the effects of ocean acidification on coral reefs

There is an interest in developing approaches to “ecosystem-based” management for coral reefs. One aspect of ecosystem performance is to monitor carbon metabolism of whole communities. In an effort to explore robust techniques to monitor the metabolism of fringing reefs, especially considering the possible effects of ocean acidification, a yearlong study of the carbonate chemistry of a nearshore fringing reef in Hawaii was conducted. Diurnal changes in seawater carbonate chemistry were measured once a week in an algal-dominated and a coral-dominated reef flat on the Waimanalo fringing reef, Hawaii, from April of 2010 until May of 2011. Calculated rates of gross primary production (GPP) and net community calcification (G) were similar to previous estimates of community metabolism for other coral reefs (GPP 971 mmol C m^?2 d^?1; G 186 mmol CaCO₃ m^?2 d^?1) and indicated that this reef was balanced in terms of organic metabolism, exhibited net calcification, and was a net source of CO₂ to the atmosphere. Average slopes of total alkalinity versus dissolved inorganic carbon (TA–DIC slope) for the coral-dominated reef flat exhibited a greater calcification-to-net photosynthesis ratio than for the algal-dominated reef flat (coral slope vs. algal slope). Over the course of the time series, TA–DIC slopes remained significantly different between sites and were not correlated with diurnal averages in reef-water residence time or solar irradiance. These characteristic slopes for each reef flat reflect the relationship between carbon and carbonate community metabolism and can be used as a tool to monitor ecosystem function in response to ocean acidification.     

Seabird abundance, biomass and prey consumption within Prydz Bay, Antarctica, 1980/1981–1992/1993

Annual observations of seabirds within Prydz Bay, East Antarctica, between the 1980/1981 and 1992/1993 seasons revealed siginificant changes in abundance of the 9 resident and 15 non-resident species. An estimated 4.85 million individual residents and 2.35 million individual non-residents were present each season. For resident and non-resident species, mean abundance was 3.75 and 1.81 birds/km², and mean biomass was 6.67 and 1.70 kg/km², respectively. Based on estimated abundances, the total consumption of marine resources by the seabird community within Prydz Bay ranged from 471,000 to 1.1 million tonnes (mean 752,000±176,000 tonnes) per 6-month summer, or between 2.02 and 4.53 kg/km² per day (mean 3.23±0.76 kg/km² per day). The mean energy flux to the seabird community within Prydz Bay each summer was 3.13*10¹² kJ, (range: 2.0*10¹² kJ–4.4*10¹² kJ), of which 66% went to the resident species. Regional abundance and biomass estimates for resident and non-resident species were both negatively correlated; when the estimated abundance and biomass of resident species were high, those of non-resident species were low. Received: 4 January 1996/Accepted: 3 July 1996     

The contribution of epipelon to total sediment microalgae in a shallow temperate eutrophic loch (Loch Leven, Scotland)

Benthic microalgae are known to perform important ecosystem functions in shallow lakes. As such it is important to understand the environmental variables responsible for regulating community structure, positioning and biomass. We tested the hypothesis that the positioning (across a depth gradient of 2–22 m overlying water depth) and relative biomass (determined using bulk and lens tissue harvested chlorophyll (Chl) a concentrations) of the epipelon community would vary independently with season (12 monthly samples) and across natural gradients of light and habitat disturbance relative to the total benthic algal community (i.e. all viable microalgae in the surface sediments) in a shallow eutrophic loch. Total sediment microalgal Chl a concentrations (TS-Chl; range: 5–874 μg Chl a g⁻¹ dw) were highest in winter and in the deepest site (20 m overlying water depth), apparently as a result of phytoplanktonic settling and sediment focussing processes. Epipelic Chl a concentrations (Epi-Chl; range: <0.10–6.0 μg Chl a g⁻¹ dw) were highest in winter/spring, a period when water clarity was highest and TS-Chl lowest. Principal components analysis highlighted strong associations between Epi-Chl and sites of intermediate depths (2.5–5.5 m) in all seasons except autumn/winter. Autumn/winter represented the season with the highest average wind speeds preceding sampling, during which the highest Epi-Chl concentrations were associated with the deepest sites. Epi-Chl was associated with intermediate light and habitat disturbance during spring/summer and summer/autumn and varied positively with habitat disturbance, only, in autumn/winter and winter/spring. The epipelon community structure also varied with depth; diatoms dominated shallow water sediments, cyanobacteria dominated deep water sediments, and sediments at sites of intermediate depth returned the highest biovolume estimates and the most diverse communities. This study has strengthened the hypothesis that the structure and biomass of benthic microalgal communities in lakes are regulated by habitat disturbance and water clarity, both of which are expected to respond to climate change and eutrophication. The degree to which these structural responses reflect functional performance requires clarification.     

Seasonal home ranges and fidelity to breeding sites among ringed seals

Population structure and patterns of habitat use among ringed seals (Phoca hispida) are poorly known, in part because seasonal movements have not been adequately documented. We monitored the movements of 98 ringed seals in the Beaufort and Chukchi seas between 1990 and 2006 using three forms of telemetry. In the winter—spring period (when the seals were occupying shorefast ice), we used radio and ultra-sonic tags to track movements above and below the ice, respectively. We used satellite-linked transmitters in summer and fall (when the seals ranged away from their winter sites) to track at-sea movements. In the shorefast ice habitat, the home ranges of 27 adult males ranged from <1 to 13.9 km² (median = 0.628) while the home ranges of 28 adult females ranged from <1 to 27.9 km² (median = 0.652). The 3-dimensional volumes used by 9 seals tracked acoustically under the ice averaged 0.07 (SD = 0.04) km³ for subadults and adult males and 0.13 (SD = 0.04) km³ for adult females. Three of the radio-tracked seals and 9 tracked by satellite ranged up to 1,800 km from their winter/spring home ranges in summer but returned to the same small (1–2 km²) sites during the ice-bound months in the following year. The restricted movements of ringed seals during the ice-bound season—including the breeding season—limits their foraging activities for most of the year and may minimize gene flow within the species.     

Evolutionary significance of the microbial assemblages of large benthic Foraminifera

Large benthic Foraminifera (LBF) are major carbonate producers on coral reefs, and are hosts to a diverse symbiotic microbial community. During warm episodes in the geological past, these reef‐building organisms expanded their geographical ranges as subtropical and tropical belts moved into higher latitudes. During these range‐expansion periods, LBF were the most prolific carbonate producers on reefs, dominating shallow carbonate platforms over reef‐building corals. Even though the fossil and modern distributions of groups of species that harbour different types of symbionts are known, the nature, mechanisms, and factors that influence their occurrence remain elusive. Furthermore, the presence of a diverse and persistent bacterial community has only recently gained attention. We examined recent advances in molecular identification of prokaryotic (i.e. bacteria) and eukaryotic (i.e. microalgae) associates, and palaeoecology, and place the partnership with bacteria and algae in the context of climate change. In critically reviewing the available fossil and modern data on symbiosis, we reveal a crucial role of microalgae in the response of LBF to ocean warming, and their capacity to colonise a variety of habitats, across both latitudes and broad depth ranges. Symbiont identity is a key factor enabling LBF to expand their geographic ranges when the sea‐surface temperature increases. Our analyses showed that over the past 66 million years (My), diatom‐bearing species were dominant in reef environments. The modern record shows that these species display a stable, persistent eukaryotic assemblage across their geographic distribution range, and are less dependent on symbiotic photosynthesis for survival. By contrast, dinoflagellate and chlorophytic species, which show a provincial distribution, tend to have a more flexible eukaryotic community throughout their range. This group is more dependent on their symbionts, and flexibility in their symbiosis is likely to be the driving force behind their evolutionary history, as they form a monophyletic group originating from a rhodophyte‐bearing ancestor. The study of bacterial assemblages, while still in its infancy, is a promising field of study. Bacterial communities are likely to be shaped by the local environment, although a core bacterial microbiome is found in species with global distributions. Cryptic speciation is also an important factor that must be taken into consideration. As global warming intensifies, genetic divergence in hosts in addition to the range of flexibility/specificity within host–symbiont associations will be important elements in the continued evolutionary success of LBF species in a wide range of environments. Based on fossil and modern data, we conclude that the microbiome, which includes both algal and bacterial partners, is a key factor influencing the evolution of LBF. As a result, the microbiome assists LBF in colonising a wide range of habitats, and allowed them to become the most important calcifiers on shallow platforms worldwide during periods of ocean warming in the geologic past. Since LBF are crucial ecosystem engineers and prolific carbonate producers, the microbiome is a critical component that will play a central role in the responses of LBF to a changing ocean, and ultimately in shaping the future of coral reefs.