Observer presence may alter the behaviour of reef fishes associated with coral colonies          下载免费PDF全文

Pedro Henrique Cipresso Pereira  Isabela Carolina Silva Leal  Maria Elisabeth de Araújo 《Marine Ecology》2016,37(4):760-769

Although underwater visual census (UVC) is the most frequently used technique for quantifying reef fish assemblages, remote video analysis has been gaining attention as a potential alternative. In the South Atlantic Ocean, Millepora spp. (class Hydrozoa) are the only branching coral species; however, little is known about the ecological role that they play for reef fish communities. We compared these two observation methods (remote video and UVC) to estimate reef fish abundance and species richness associated with colonies of the fire‐coral Millepora alcicornis at Tamandaré Reefs, Northeast Brazil. Additionally, the two different techniques were used to compare species behaviour in association with fire‐corals in order to examine the biases associated with each technique and provide useful information for behavioural ecologists studying fish–coral associations. There were no differences in reef fish abundance or species richness sampled by remote video or UVC. However, a significant difference in the behaviour of associated fish was recorded between the two methods. In the presence of a diver carrying out a UVC, fish were observed spending more time sheltered amongst the coral branches compared with passively swimming on coral colonies with the remote video technique. Specifically, on the remote video recordings agonistic interactions between fish and passive swimming accounted for 33.3% and 22.2% of the census time, respectively. By comparison, when observed by a diver fish spent 34.8% of their time sheltering amongst the coral branches. We demonstrate that both techniques are similarly effective for recording fish abundance and species richness associated with fire‐corals. However, differences were observed in the ability of each method to detect the behaviour of coral‐associated fishes. Our findings show that behavioural ecologists studying complex fish–coral associations need to ensure that their aims are clearly defined and that they choose the most appropriate technique for their study in order to minimize methodological biases.  相似文献   

Sublittoral seaweed communities on natural and artificial substrata in a high-latitude coral community in South Africa     

L Gersun  JR Hart  GW Maneveldt  JJ Bolton 《African Journal of Marine Science》2016,38(3):303-316

Coral mortality may result in macroalgal proliferation or a phase shift into an alga-dominated state. Subtidal, high-latitude western Indian Ocean coral communities at Sodwana Bay on the KwaZulu-Natal coast, South Africa, have experienced some mortality because of warm-water anomalies, storms and other causes, but the response of the macroalgae is unknown. We investigated the abundance and diversity of benthic algae on different hard natural substrata (dead digitate, brain and plate corals and beach rock) on Two-Mile Reef, Sodwana Bay. We also compared algal communities colonising ceramic, marble and pretreated ceramic tiles placed on the reef for six months. We identified 95 algae (14 Chlorophyta, 11 Phaeophyceae, 69 Rhodophyta and one cyanobacterium). Assemblages on natural and artificial substrata were dominated by the brown alga Lobophora variegata (Lamouroux) Womersley ex Oliveira and non-geniculate corallines (Rhodophyta, Corallinaceae). Cluster and ordination analyses revealed that the algae showed no affinity for particular substrata, whether natural or artificial. Algal cover was occasionally higher on rougher tiles and crustose corallines were significantly more abundant on marble than ceramic tiles. Two-Mile Reef had 23.1% dead and 48.4% live scleractinian coral cover, where dead corals were colonised indiscriminately by many small algal species, but there was no evidence of algal proliferation. The results provide a baseline for monitoring this high-latitude reef system.  相似文献   

A seasonal comparison of prokaryote numbers,biomass and heterotrophic productivity in waters of the KwaZulu-Natal Bight,South Africa     

D Muir  T Kunnen 《African Journal of Marine Science》2016,38(1):S123-S138

The KwaZulu-Natal Bight is a shallow indentation of the eastern seaboard of South Africa, characterised by a narrow (45 km wide) extension of the continental shelf, with a shelf break at about 100 m. It has a complex hydrography: the waters of the bight are derived from the fast-flowing, southward-trending Agulhas Current, which is fed mostly by the tropical and subtropical surface waters of the South-West Indian Ocean subgyre, which are generally oligotrophic in nature, notably depleted in reduced nitrogen and phosphate except at river mouths and during periodic upwelling of deeper nutrient-rich water. Despite this, the bight is believed to be relatively productive, and it is suggested that efficient nutrient recycling by prokaryotes may sustain primary productivity efficiently, even in the absence of new nutrient inputs. Here we have measured bacterial numbers, biomass and heterotrophic productivity during summer and winter in conjunction with phytoplankton standing stock and factors that influence it. Bacterial distribution closely matched phytoplankton distribution in surface waters, and was highest close to the coast. Bacterial standing stocks were similar to those of oligotrophic systems elsewhere (0.5–5.0 × 10⁵ cells ml^–1; 1 × 10^–8 to 1.25 × 10^–7 g C ml^–1) and increased in association with the development of phytoplankton blooms offshore and with inputs of allochthonous material by rivers at the coast. Heterotrophic productivity in summer was lowest in the far south and north of the bight (0.5 × 10^–10 g C ml^–1 h^–1) but higher close to the shore, over shallow banks, and in association with increased phytoplankton abundance over the midshelf (1.0–3.5 × 10^–9 g C ml^–1 h^–1). There were marked seasonal differences with lower bacterial standing stocks (5 × 10⁴ to 2 × 10⁵ cells ml^–1; 4–5 × 10^–9 to 1–2 × 10^–8 g C ml^–1) and very low bacterial productivity (4 × 10^–11 to 1 × 10^–10 g C ml^–1 h^–1) in winter, probably resulting from lowered rates of primary productivity and dissolved organic matter release as well as reduced riverine allochthonous inputs during the winter drought.  相似文献   

北极斯瓦尔巴特群岛及邻区天然气水合物分解对气候、海洋环境和生物的影响     

聂云峰  于晶  陈宏文  万玲  范广慧  房强  吴怀春 《现代地质》2018,32(5):1012

天然气水合物是一种潜在的巨量能源,但其分解释放的甲烷可能对全球气候与海洋环境产生巨大影响。然而,人们目前对天然气水合物分解产生的环境和生物效应的了解还不够全面。北极地区的斯瓦尔巴特群岛及邻区的海底和冻土层中蕴含大量甲烷,对气候变化十分敏感,是人们研究天然气水合物对气候变化的响应机制和其分解对生态环境影响的绝佳场所。系统总结了斯瓦尔巴特群岛及邻区水合物分解的气候与环境效应,发现目前研究区水合物分解产生的甲烷进入大气的年际通量不大,对全球气候的影响可能有限;水合物分解对海底滑坡起到催化剂的作用,但不是首要因素;海底水合物分解释放的甲烷能打破原有的化学平衡、生产力分布规律与输送机制、生物耦合关系甚至不同栖息地间的连通性,进而影响底栖生物群落。这些认识对研究天然气水合物开采对生态环境可能造成的影响和采取相应防治措施具有一定的借鉴意义。  相似文献   

河流景观生态学的发展与当前核心议题          下载免费PDF全文

薛兴华  钱华 《水科学进展》2018,29(6):887-897

河流景观生态学已成为河流科学研究与应用的新范式,但国内研究还颇为不足。从河流景观生态学发展的逻辑必然性、主要进程、基本内容与重要理论等方面进行了总结。结果显示,多尺度跨学科整体论河流认识要求和景观尺度上处理河流问题的实践需求共同推动河流景观生态学的迅速发展,其中心议题是河流物理景观系统与生物系统在不同等级尺度上的结构、格局与功能过程,尤其重视物理景观与不同等级生物系统的相互作用关系,对河流景观多尺度等级性、高动态性和有向性等突出性质的认识已取得重要理论发展。指出当前面临5个方面的核心议题亟需取得突破:改进和统一河流景观分类系统、河流景观跨尺度研究、河流景观方法对经典河流生态理论的再认识、河流景观机理与模拟、河流景观对气候变化与区域土地利用/覆被变化的响应研究。  相似文献   

松嫩平原东部土地利用时空动态变化分析   总被引：1，自引：0，他引：1  

杨佳佳  张一鹤  冯雨林  高铁  肖红叶  刘洋  杨泽  魏明辉  张哲寰 《地质与资源》2021,29(6):627

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Long-term effects of a toxic algal bloom on subtidal soft-sediment macroinvertebrate communities in Wellington Harbour, New Zealand   总被引：3，自引：1，他引：2  

Kerstin Krger  Jonathan P.A. Gardner  Ashley A. Rowden  Robert G. Wear 《Estuarine, Coastal and Shelf Science》2006,67(4):589-604

The long-term effects (>1 year) of a naturally occurring toxic plankton bloom (Karenia brevisulcata) on subtidal benthic macroinvertebrate communities were investigated in Wellington Harbour, a semi-enclosed temperate embayment in New Zealand. For 3 years communities were sampled at three different sites in the harbour. Analyses revealed that community recovery following the bloom was site-specific. Multivariate analyses indicated that at one site community composition was approaching recovery 3 years post-bloom. At the second site, a sequential recovery process was indicated, whereas at the third site the community composition oscillated from year to year, but did not show any signs of a sequential recovery process. The nature of the hydrodynamic regime was identified as a major factor influencing the observed recovery processes. Communities exposed to an active hydrodynamic regime were less affected by the bloom and differed little in their composition pre- and post-bloom, as they were naturally in a perpetual state of recovery as indicated by a dominance of r-selected species. The community at the hydrodynamically less active site was more affected by the bloom and exhibited temporal differences in composition consistent with successional models. Complete recovery to a pre-disturbance climax community dominated by K-selected species is likely to take 4–5 years, if not interrupted by other disturbances. Given the increased occurrence of harmful algal blooms worldwide, more monitoring and manipulative studies are needed to further evaluate the effects of such disturbances on macrobenthic communities.  相似文献   

Carbon cycling in a high-arctic marine ecosystem – Young Sound, NE Greenland     

Sren Rysgaard  Torkel Gissel Nielsen 《Progress in Oceanography》2006,71(2-4):426

Young Sound is a deep-sill fjord in NE Greenland (74°N). Sea ice usually begins to form in late September and gains a thickness of 1.5 m topped with 0–40 cm of snow before breaking up in mid-July the following year. Primary production starts in spring when sea ice algae begin to flourish at the ice–water interface. Most biomass accumulation occurs in the lower parts of the sea ice, but sea ice algae are observed throughout the sea ice matrix. However, sea ice algal primary production in the fjord is low and often contributes only a few percent of the annual phytoplankton production. Following the break-up of ice, the immediate increase in light penetration to the water column causes a steep increase in pelagic primary production. Usually, the bloom lasts until August–September when nutrients begin to limit production in surface waters and sea ice starts to form. The grazer community, dominated by copepods, soon takes advantage of the increased phytoplankton production, and on an annual basis their carbon demand (7–11 g C m⁻²) is similar to phytoplankton production (6–10 g C m⁻²). Furthermore, the carbon demand of pelagic bacteria amounts to 7–12 g C m⁻² yr⁻¹. Thus, the carbon demand of the heterotrophic plankton is approximately twice the estimated pelagic primary production, illustrating the importance of advected carbon from the Greenland Sea and from land in fuelling the ecosystem.In the shallow parts of the fjord (<40 m) benthic primary producers dominate primary production. As a minimum estimate, a total of 41 g C m⁻² yr⁻¹ is fixed by primary production, of which phytoplankton contributes 15%, sea ice algae <1%, benthic macrophytes 62% and benthic microphytes 22%. A high and diverse benthic infauna dominated by polychaetes and bivalves exists in these shallow-water sediments (<40 m), which are colonized by benthic primary producers and in direct contact with the pelagic phytoplankton bloom. The annual benthic mineralization is 32 g C m⁻² yr⁻¹ of which megafauna accounts for 17%. In deeper waters benthic mineralization is 40% lower than in shallow waters and megafauna, primarily brittle stars, accounts for 27% of the benthic mineralization. The carbon that escapes degradation is permanently accumulated in the sediment, and for the locality investigated a rate of 7 g C m⁻² yr⁻¹ was determined.A group of walruses (up to 50 adult males) feed in the area in shallow waters (<40 m) during the short, productive, ice-free period, and they have been shown to be able to consume <3% of the standing stock of bivalves (Hiatella arctica, Mya truncata and Serripes Groenlandicus), or half of the annual bivalve somatic production. Feeding at greater depths is negligible in comparison with their feeding in the bivalve-rich shallow waters.  相似文献   

转型期上海社会空间分异研究   总被引：75，自引：14，他引：61  

李志刚  吴缚龙 《地理学报》2006,61(2):199-211

采用2000年第五次全国人口普查数据库中居民委员会尺度的数据,对转型期上海城市空间重构与分异展开研究。存在6类社会区：计划经济时代建设的工人居住区、外来人口集中居住区、白领集中居住区、农民居住区、新建普通住宅居住区、离退休人员集中居住区。通过计算分异指数,发现当前上海存在严重的住房分异;但并不存在明显的以社会经济属性为基础的社会空间分异。造成这一现象的原因在于计划经济时代的历史以及仍然存在的大型企事业单位对住房的影响。中国城市目前的社会空间分异在程度上与西方城市还有根本的差异。  相似文献   

鲍育苗生物学中饵料硅藻的相关研究进展   总被引：3，自引：0，他引：3  

徐力文  刘广锋  王江勇 《海洋科学进展》2006,24(4):611-617,618

底栖硅藻是鲍育苗阶段不可缺少的饵料,也是诱导鲍浮游幼体附着和变态的重要物质,硅藻的种类、营养价值、生态状况等对幼体的附着变态及其后以微藻为饵料阶段的生长率和成活率都有至关重要的影响。总结近10a国内外与饵料硅藻相关的研究概况,包括硅藻对鲍附着变态、生长率和成活率的影响;鲍幼苗饵料转化与消化器官发育的关系;影响硅藻营养的生理生化因子;与鲍幼苗掉板死亡相关的藻类研究等,为鲍育苗生物学的研究提供借鉴和参考。  相似文献