Habitat Differences in Marine Invasions of Central California

We carried out a two-part investigation that revealed habitat differences in marine invertebrate invasions. First, we compared invasion levels of hard vs soft substrata in Elkhorn Slough, an estuary in Central California, by comparing abundance and richness of native vs exotic species in quantitative samples from each habitat type. Our results revealed that the hard substrata were much more heavily invaded than the soft substrata. Nearly all the hard substrata in Elkhorn Slough, as in most estuaries along the Pacific coast of North America, are artificial (jetties, rip-rap, docks). Some exotic species may by chance be better adapted to this novel habitat type than are natives. Two major vectors responsible for marine introductions, oyster culturing and ship-hull fouling, are also more likely to transport species associated with hard vs soft substrata. Secondly, we compared estuarine and open coast invasion rates. We examined species richness in Elkhorn Slough and adjacent rocky intertidal habitats along the Central California coast. The absolute number of exotic species in the estuary was an order of magnitude higher than along the open coast (58 vs 8 species), as was the percentage of the invertebrate fauna that was exotic (11% vs 1%). Estuaries on this coast are geologically young, heavily altered by humans, and subject to numerous transport vectors bringing invasive propagules: all these factors may explain why they are strikingly more invaded than the open coast. The finding that the more species rich habitat – the open coast – is less invaded is in contrast to many terrestrial examples, where native and exotic species richness appear to be positively correlated at a broad geographic scale.     

Edward Smith Deevey 1914–1988

Stone loach and bullhead were given a choice of Chironomus and Asellus prey in experiments using solitary fish and fish in company. Solitary fish ate more than fish in company. The effect of light and substratum type on feeding was investigated. Both species ate more prey items on gravel than silt when a significant difference was observed. Bullhead ate more than loach in the light on both substrata. The only experiment in which loach ate more than bullhead was on a silt substratum in the dark. It is concluded that these two species utilise different components of the available food resources in chalk streams by adopting different habitats.     

Validation of a randomization procedure to assess animal habitat preferences: microhabitat use of tiger sharks in a seagrass ecosystem

1. Tiger sharks Galeocerdo cuvier are important predators in a variety of nearshore communities, including the seagrass ecosystem of Shark Bay, Western Australia. Because tiger sharks are known to influence spatial distributions of multiple prey species, it is important to understand how they use habitats at a variety of spatial scales. We used a combination of catch rates and acoustic tracking to determine tiger shark microhabitat use in Shark Bay. 2. Comparing habitat-use data from tracking against the null hypothesis of no habitat preference is hindered in Shark Bay, as elsewhere, by the difficulty of defining expected habitat use given random movement. We used randomization procedures to generate expected habitat use in the absence of habitat preference and expected habitat use differences among groups (e.g. males and females). We tested the performance of these protocols using simulated data sets with known habitat preferences. 3. The technique correctly classified sets of simulated tracks as displaying a preference or not and was a conservative test for differences in habitat preferences between subgroups of tracks (e.g. males vs. females). 4. Sharks preferred shallow habitats over deep ones, and preferred shallow edge microhabitats over shallow interior ones. The use of shallow edges likely increases encounter rates with potential prey and may have profound consequences for the dynamics of Shark Bay's seagrass ecosystem through indirect effects transmitted by grazers that are common prey of tiger sharks. 5. Females showed a greater tendency to use shallow edge microhabitats than did males; this pattern was not detected by traditional analysis techniques. 6. The randomization procedures presented here are applicable to many field studies that use tracking by allowing researchers both to determine overall habitat preferences and to identify differences in habitat use between groups within their sample.     

闽江河口潮汐湿地二氧化碳和甲烷排放化学计量比

为了阐明河口潮汐湿地碳源温室气体排放的化学计量比特征,对闽江河口潮汐湿地二氧化碳和甲烷排放进行了测定与分析。结果表明:芦苇湿地和短叶茳芏湿地二氧化碳与甲烷排放均呈现正相关;涨潮前、涨落潮过程和落潮后芦苇湿地和短叶茳芏湿地CO2∶CH4月平均值分别为55.4和185.0,96.3和305.5,68.7和648.6,3个过程芦苇湿地和短叶茳芏湿地CO2∶CH4差异均不显著(P>0.05),2种植物湿地CO2∶CH4对潮汐的响应并不一致,但均在涨潮前表现为最低;涨潮前、涨落潮过程和落潮后均表现为芦苇湿地CO2∶CH4低于短叶茳芏湿地(P<0.05);河口潮汐湿地CO2∶CH4为空间变异性>时间变异性,潮汐、植物和温度均对CO2∶CH4的变化具有一定的调节作用。     

闽江口潮滩湿地不同植被带土壤及间隙水中硅的分布特征

以闽江口潮滩湿地为研究对象,由岸及海方向对芦苇、短叶茳芏、互花米草(潮沟内)和互花米草(潮沟外)4种湿地土壤生物硅和土壤间隙水氮硅营养盐含量及其随深度变化的特征进行为期1a的季度观测。结果显示:互花米草(外)、短叶茳芏、芦苇和互花米草(内)带湿地土壤生物硅的年均含量依次降低,分别为14.33、10.40、9.98、7.50 mg/g;互花米草(外)、互花米草(内)、短叶茳芏和芦苇带湿地土壤间隙水活性硅酸盐年均含量依次降低,分别为407、359、344、323μmol/L;湿地各植被带土壤及间隙水含硅量均呈现夏秋季节高于冬春季节的趋势。统计分析表明:间隙水活性硅酸盐与土壤生物硅含量、距潮沟的距离之间的正相关性均比较显著(P0.05),温度对土壤中硅含量的影响也有一定的正相关性,说明湿地植被、温度和潮汐作用是影响闽江口湿地硅分布的重要因素。与土著种对比,互花米草入侵在一定程度上改变了闽江口潮滩湿地土壤硅分布的格局。     

闽江河口短叶茳芏潮汐湿地甲烷排放通量

采用静态箱-气相色谱法,测定了闽江河口短叶茳芏（Cyperus malaccensis）潮汐湿地甲烷排放通量.结果表明：夏季和冬季短叶茳芏潮汐湿地甲烷排放通量的日变化范围分别在1.29～2.93 mg·m^-2·h^-1和0.06～0.22 mg·m^-2·h^-1;涨潮前、涨落潮过程中和落潮后甲烷排放通量分别在0.11～1.52 mg·m^-2·h^-1、0.10～1.05 mg·m^-2·h^-1和0.05～1.70 mg·m^-2·h^-1,月平均值分别为0.73、0.47和0.72 mg·m^-2·h^-1,其排放峰值均出现在9月,最低值出现在3月,涨落潮过程中的甲烷排放通量明显低于涨潮前和落潮后（P< 0.05）;甲烷排放通量的季节变化表现为：夏季>秋季>春季>冬季;潮汐是影响甲烷排放日变化的重要因子,植物生长阶段和温度是甲烷排放月变化和季节变化的主要控制因子.     

The feeding strategy of dab Limanda limanda in the southern North Sea: linking stomach contents to prey availability in the environment

The feeding strategy of dab Limanda limanda was investigated within a predefined research area in the southern North Sea for 2 years. The aims were: 1) to establish the relationship between prey availability and dab abundance, distribution, body condition and prey selection, and 2) to determine the underlying functional processes of prey choice in dab. Temporal and spatial trends of prey availability in relation to dab abundances, distribution, condition and prey selection were analysed. Temporal trends in dab condition, percentage of empty stomachs and numbers of ingested prey were apparent. In particular in the winter period 2000–2001 dab were in poor condition and prey items were only rarely found in stomachs. Similarly prey availability decreased in the environment while the abundance of dab increased. Thus, temporal changes in the nutritive state were partly thought to be attributed to density‐dependent effects. The stomach composition of dab during the two consecutive summers was mainly dominated by Pariambus typicus and Ophiura albida while in the winter period only O. albida made a significant contribution to the stomach content. Analysis of prey characteristics indicated that only prey densities in the environment significantly influenced prey choice in dab, while other characteristics such as the position of the prey in the habitat, its palatability or mobility did not have significant effects. The feeding strategy of dab thus was highly opportunistic, although trends were apparent that suggested that buried living fauna was less likely to be ingested, which was also observed in previous studies.     

Seasonal variation in nitrous oxide and methane emissions from subtropical estuary and coastal mangrove sediments, Australia

Mangrove sediments can act as sources of the greenhouse trace gases, nitrous oxide (N(2) O) and methane (CH(4) ). Confident reporting of trace gas emissions from mangrove sediments at local levels is important for regional emissions inventories, since small changes in N(2) O and CH(4) fluxes greatly influence greenhouse gas budgets due to their high global warming potentials. It is also important to identify the drivers of trace gas emission, to prioritize management for minimising emissions. We measured N(2) O and CH(4) fluxes and abiotic sediment parameters at midday low tide in winter and summer seasons, at four sites (27°33'S, 152°59'E) ranging from estuary to ocean sub-tropical mangrove sediments, having varied anthropogenic impacts. At all sites, sediment N(2) O and CH(4) emissions were significantly lower during winter (7-26 μg N(2) O m(-2) · h(-1); 47-466 μg CH(4) m(-2) · h(-1)) compared to summer (28-202 μg N(2) Om(-2) · h(-1); 247-1570 μg CH(4) m(-2) · h(-1)). Sediment temperature, ranging from 18 to 33°C, strongly influenced N(2) O and CH(4) emissions. Highest emissions (202 μg N(2) O m(-2) · h(-1), 1570 μg CH(4) m(-2) · h(-1) ) were detected at human-impacted estuary sites, which generally had higher total carbon (<8%) and total nitrogen (<0.4%) in sediments and reduced salinity (<16 dS · m(-1)). Large between-site variation highlights the need for regular monitoring of sub-tropical mangroves to capture short-lived, episodic N(2) O and CH(4) flux events that are affected by sediment biophysico-chemical conditions at site level. This is important, particularly at sites receiving anthropogenic nutrients, and that have variable freshwater inputs and tidal hydrology.     

互花米草入侵对黄河口潮沟形态特征和植物群落分布的影响

互花米草大规模入侵滨海湿地,对潮沟形态特征和植物群落的演变产生重大影响.本研究基于2008-2020年遥感影像,利用3S技术,结合回归分析与统计分析法,分析黄河口湿地互花米草入侵的演变特征,探究其对潮沟形态特征和植物群落分布的影响.结果 表明:2008年以来,黄河口互花米草面积增长迅速,增长速度为4.47 km2·a-...     

基于物种落差分析的公园鸟类多样性提升设计——以湖南常德螺湾湿地公园为例

随着城市化发展,许多公园鸟类栖息环境遭受破坏,导致当前的鸟类多样性与历史上的和周边的都存在较大差异,为此,我们从项目区域的当前-周边-历史三者间在鸟类物种及其栖息地上的落差分析入手,以此确定目标物种及其栖息地,并加以归类,从而有针对性地进行相关设计。2016年5月至2017年3月在湖南常德柳叶湖螺湾湿地公园开展的鸟类多样性提升设计中,通过实地调查并结合文献查阅,记录到项目区域16种,周边79种,历史上146种鸟类,运用三者间的物种落差分析法确定主要的21种可恢复目标物种和4种栖息地类型,结合项目区域及周边空间特点,将项目区域划分为4个区域,在各区域内设计并营建相应的栖息地,再配套采用多种鸟类招引措施。至2017年3月,项目区鸟类已可实地观察到39种,并于2017年12月吸引到超过2000只的野鸭群来此越冬。以上实际效果表明,设计有效地提升了湿地公园鸟类多样性且增加了景观要素,可充分发挥生物保护功能。     

基于栖息地风险评价模型的海岸带滩涂湿地风险评价——以闽三角为例

海岸带湿地是生物多样性最丰富、生产力最高、最具价值的生态系统之一。然而近年来,随着城市化和工业化进程的加快,我国海岸带地区的土地利用正发生深刻变化,生态风险凸显。利用2000、2005、2010和2015年的Landsat TM/ETM+和Landsat 8 OLI遥感影像,融合行政区划图与地形图,并引入一个评价多元海洋、海岸带利用对栖息地造成风险的模型,即Integrated Valuation of Ecosystem Services and Trade-offs(In VEST)模型中的栖息地风险评价(Habitat Risk Assessment,HRA),模型评价闽三角海岸带滩涂湿地的生态风险。结果表明:(1)闽三角海岸带滩涂湿地风险以低风险为主;(2)泉州地区的风险面积最大(约4389.91 hm~2),漳州地区最小(约4630.73 hm~2);(3)修正面积影响的情况下,其他建设用地造成的暴露和影响较大,耕地造成的暴露和影响最小。不同区域滩涂湿地风险程度的可视化表达,可以揭示滩涂湿地高风险地区以及高风险的产生原因,便于管理者对滩涂湿地采取精准的保育措施。     

Contrasting effects of habitat fragmentation,population density,and prey availability on body condition of two orb‐weaving spiders

1. Habitat fragmentation is a major threat to biodiversity because it disrupts movement between habitat patches. In addition, arthropod fitness may be reduced in fragmented habitats, e.g. due to reduced prey availability. 2. We studied the relationship of spider body condition with habitat fragmentation, population density, and prey availability. We expected that prey availability and population density of spiders would be affected by landscape composition and patch isolation. Body condition should be enhanced by high prey availability, but negatively affected by population density due to competition. 3. We sampled spiders on 30 groups of cherry trees that varied independently in the level of isolation from other woody habitats and in the percentage of woody habitat within 500 m radius. As a measure of body condition, we used residuals of the relationship between individual body mass/opisthosoma width and prosoma width of the two most common orb‐weaving spider species, Nuctenea umbratica Clerck and Araniella opisthographa Kulczynski. 4. Body condition of A. opisthographa was positively correlated with the abundance of flies, which increased with the percentage of forest in the landscape. In contrast, body condition of N. umbratica was reduced at high population densities, presumably due to intraspecific competition. In addition, body condition and population density of A. opisthographa was lower at isolated sites. 5. Our study suggests that effects of landscape fragmentation on body condition vary strongly between spider species, depending on the relative role of food limitation and intraspecific competition.