Temporal Variation In Biomass Research Articles

芡实分区刈割试验对陈瑶湖后生浮游动物群落结构的影响

陈瑶湖流域是长江中下游重要的水禽省级自然保护区，近年来随着农业的发展，湖区存在芡实种植过密，汛期影响行洪的隐患，对湖区的水生态系统结构与功能的稳定性造成严重影响。为研究芡实分区刈割试验对陈瑶湖后生浮游动物群落结构的影响，于2019年8月期间对陈瑶湖后生浮游动物进行调查。共鉴定出后生浮游动物15科22属40种，其中轮虫12属26种，枝角类8属11种，桡足类2属3种，群落结构主要以轮虫为主，后生浮游动物种类分布时空上无显著差异（P>0.05）。共发现优势种8属10种，分别为萼花臂尾轮虫（Brachionus calyciflorus）、角突臂尾轮虫（Brachionus angularis）、剪形臂尾轮虫（Brachionus forficula）、螺形龟甲轮虫（Keratella cochlearis）、囊形单趾轮虫（Monostyla bulla）、蹄形腔轮虫（Lecane ungulata）、针簇多肢轮虫（Polyarthra trigla）、迈氏三肢轮虫（Filinia maior）、长额象鼻溞（Bosmina longirostris）和广布中剑水蚤（Mesocyclops leuckarti）。后生浮游动物密度和生物量平均值分别为（1681.49±205.73）个/L和（7.8±1.52） mg/L，密度和生物量峰值均出现在初期的未刈割区，最低值均出现在后期的河道。后生浮游动物密度的空间分布呈现未刈割区 > 刈割区 > 河道的特征，时间变化呈现刈割初期 > 前期 > 中期 > 后期的趋势，生物量的时空变化趋势与密度一致。ShannonWiener多样性指数、Margalef丰富度指数和Pielou均匀度指数变化范围分别为1.67-3.42、1.64-3.57和0.41-1.13.统计分析结果表明TN、TP、NH₄⁺-N、Chl.a、EC和SD是影响浮游动物群落结构的主要因子。综合生物和理化指标判别陈瑶湖水体已处于中污染状态；营养状态参数结果表明，陈瑶湖已处于中度富营养状态。;Chenyao Lake basin is an important waterfowl Provincial Nature Reserve in the middle and lower reaches of the Yangtze River,In recent years, with the development of agriculture, there are some hidden dangers in the lake area, such as planting too much Euryale ferox, affecting the flood discharge in flood season, and seriously affecting the stability of the structure and function of the aquatic ecosystem in the lake area.In order to study the effects of mowing experiment in different areas of Euryale ferox on the community structure of metazoan zooplankton in Chenyao Lake, the metazoan zooplankton was investigated in August 2019. A total of 40 species of metazooplankton belonging to 22 genera, 15 families were identified. Among them, 26 species belong to 12 genera of Rotifer, 11 species belong to 8 genera of Cladocera and 3 species belong to 2 genera of Copepoda,The community structure was dominated by Rotifers,There was no significant difference in the spatial and temporal distribution of metazoan zooplankton (P>0.05). A total of 8 genera and 10 species of dominant species were found,including Brachionus calyciflorus, B. angularis, B. forficula,Keratella cochlearis, Monostyla bulla, Lecane ungulata, Polyarthra trigla, Filinia maior, Bosmina longirostris and Mesocyclops leuckarti. The average animal density and biomass of metazoan zooplankton were (1681.49 +205.73) ind/L and (7.8+1.52) mg/L respectively,The peak values of density and biomass appeared in the initial stage of no mowing area and the lowest values all appeared in the later stage of channel.The spatial distribution of the density of metazoan zooplankton showed the characteristics of no mowing area > mowing area > river channel, while the temporal change trend was in the initial stage > early stage > middle stage > late stage. The trend of spatial and temporal variation in biomass and density was consistent. The Shannon Wiener diversity index, Margalef richness index and Pielou evenness index of the metazoan zooplankton community were 1.67-3.42, 1.64-3.57 and 0.41-1.13, respectively. The results of Redundancy analysis and Pearson correlation analysis showed that TN, TP, NH₄⁺-N, Chl a, EC and SD were the main factors affecting the community structure of zooplankton. According to the comprehensive biological and physical and chemical indicators, Chenyao Lake was in a state of moderate pollution. The results of nutritional parameters indicated that Chenyao Lake was in a state of moderate eutrophication.

Spatial Appraisal of the Impacts of Drought on Agricultural Patterns in Karachi

This paper is aimed at studying the spatial changes in agricultural patterns practiced in the suburbs of Karachi, which is the most densely populated city of Pakistan with high food demands of the inhabitants. This study deals mainly with Physical factors primarily climatic indicators to observe and analyze the changes in the pattern of agricultural production and the types of crops in last 20-30 years. Variability of climate when coupled with anthropogenic factors play important role in the acceleration of problems for farmers. Trends of associated agricultural output observed in different years of high and low rainfall. This study has successfully demonstrated inquisitive approach by using published secondary data from governmental sources and ground verification in recent times. Temporal variation in biomass, was found dependent upon pattern of rainfall and temperature etc. Study reveals that there are clear signs of desertification and drought in the study area.

Biological evaluation of an existing spatial management network for an exploited penaeid species

Spatial management may be employed to achieve objectives aimed at maintaining or enhancing productivity and sustainability of exploited populations. Spatial management is used in penaeid fisheries to alter the spatiotemporal distribution of fishing effort to achieve outcomes such as avoidance of undesirable size-classes. Eastern King Prawn (Penaeus [melicertus] plebejus; EKP) is a valuable penaeid species for which harvest is supported by an extensive spatial management network, however these closures have never been evaluated. We examine temporal variation in biomass and size structures within three trawl closure areas spanning four degrees of latitude. There was substantial spatial variation in EKP biomass among locations, fished and non-fished zones and sampling periods, which appeared to be influenced by depth, temperature and distance to the adjacent estuarine nursery. Size structure varied among locations and sampling periods, and differed inside and outside of closure areas, however in many cases the majority of prawns that were protected within closure areas were consistently smaller than the estimated size at first capture for optimal yield per recruit. The data suggest that the closures are likely to be effective at achieving their objective, but there may be some scope for adaptive management.

Frequent upwelling intrusions and rainfall events drive shifts in plankton community in a highly eutrophic estuary

Seasonal upwelling and rainfall events influence estuarine communities, but their interaction is not well understood, particularly in estuaries impacted by coastal eutrophication. Here we evaluated the responses of the plankton community to multiple drivers in Guanabara Bay, a eutrophic estuary in the western Atlantic influenced by coastal upwelling. Plankton taxonomy and biomass were determined through weekly sampling over 1-year. The presence of the South Atlantic Central Water (SACW) signature was detected in the bay in half of our samples during the wet season. Importantly, SACW intrusions derived from coastal upwelling had a significant impact on plankton community composition. For microplankton, taxonomic shifts reflected in different cell sizes, with larger mixotrophic and heterotrophic taxa characterizing SACW intrusions. Larger species of copepods, including indicators of SACW, were also associated to the upwelling intrusion. Overall, plankton biomass was not explained by the SACW presence or absence alone; instead, the interaction between rainfall and upwelling was key to determine temporal variations in biomass. Our findings suggest that SACW intrusions can impact food web functioning through shifts in community composition and size depending on the relative intensity and frequency of upwelling events and rainfall. Frequent SACW intrusions might also dilute the highly eutrophic waters, with the potential to shift the metabolism of an estuary heavily impacted by eutrophication.

Coralline macroalgae contribution to ecological services of carbon storage in a disturbed seagrass meadow

Coralline macroalgae are globally distributed rhodopyhtes that remove carbon from their immediate environment and transform it into carbonate sediments through the senescence of their calcified tissues. In this study, the calcium carbonate (CaCO3) stocks in the tissue of Jania adhaerens and sediments in Tanjung Adang Shoal, Johor were quantified for a 13-month study period. The detailed maps of the geographical distribution based on the spatial and temporal variations of biomass and CaCO3 were also assessed. The highest amount of biomass, CaCO3 and organic carbon (OC) stocks in the tissues showed the highest in May 2018 and May 2019. The biomass values ranged from 65 to 143 g DW m−2, which contained 53–147 g CaCO3 m−2 and 3–11 g OC m−2. These findings provided insights into the biogeochemical cycling of these inputs, which can be used to estimate the overall carbon budget of the macrophyte meadow.

Supply and Consumption of Household Energy in Central Ethiopia: The Case of Debre Berhan Town

Energy crisis resulting from complete dependency on biomass fuel is becoming a major challenge for the conservation of forest resources in Ethiopia. The aim of this study was to quantify the main biomass fuel supply and also examine the household energy consumption pattern in Debre Berhan town, Ethiopia. It was hypothesized that there is spatial and temporal variation of biomass fuel entering into the town. Moreover, it was expected that socioeconomic variables affect the energy consumption pattern at a household level. Point census was conducted to quantify the amount of biomass fuel brought into the town. As a complement, a structured questionnaire comprised of open- and closed-ended questions was developed and administered to a total of 117 households. This was carried out to collect information on domestic energy consumption pattern in the town. The results revealed that the amount of biomass fuel brought into the town was significantly affected by spatial and temporal factors. Compared with the Addis Ababa direction, the amount of fuel wood brought into the town from Dessie point of entry was statistically higher. Moreover, the amount of biomass fuel entering the town during the market days was significantly greater than that of the non-market days. The multiple linear regression models revealed that several socioeconomic variables significantly affected ‘the shortage of energy supply for household consumption’ and ‘the energy consumption pattern at a household level’ in the town. The results revealed that there is a remarkable deficiency of energy supply in the town. Therefore, creating public awareness about natural resources conservation, disseminating energy-efficient technologies (e.g. energy saving stoves), issuing strict government energy policy and providing alternative energy from the government with less taxation may decrease the undesirable consequences of environmental degradation.

Multibeam sonar water column data processing tools to support coastal ecosystem science

Multibeam sonar water column data are routinely collected by hydrographic survey vessels to observe and validate minimum depth measurements over anthropogenic submerged objects, which may pose a hazard to navigation. A large volume of additional data is collected during this process but mostly goes unused. This project investigates the development of processing tools and algorithms to automate the extraction of oceanographic and ecological features from the water column data files to enhance the usefulness of these datasets. Sample data from a Gulf of Mexico Research Initiative (GoMRI) project is explored where multibeam data is collected simultaneously with a towed profiling high resolution in situ ichthyoplankton imaging system (with CTD, dissolved oxygen, PAR, and chlorophyll-a fluorescence sensors). The objective is to identify and map spatial and temporal variations in biomass throughout the water column by correlating the acoustic data with imagery and sensor output from the towed profiling system. ...

Herbivores control effects of algal species richness on community biomass and stability in a laboratory microcosm experiment

Hundreds of studies that have explored how biodiversity affects the productivity and stability of ecosystems have produced a consensus that communities composed of more species tend to have higher biomass that is more stable through time. However, the majority of this work stems from studies performed using highly simplified food webs, often composed of just primary producers competing for inorganic resources in the absence of trophic interactions. When studies have incorporated trophic interactions, diversity‐function relationships have been more variable, leaving open the question of how biodiversity affects the functioning of ecosystems with more trophic levels. Here we report the results of a laboratory experiment that used freshwater microcosms to test for effects of algal diversity (one or four species) on community biomass and temporal variability in the presence and absence of two different herbivore species (cladocerans Ceriodaphnia dubia and Daphnia pulex). When no herbivores were present, we found the classic pattern observed in hundreds of other studies – as species richness of algae increased, algal biomass increased, and the temporal variation in biomass decreased. This pattern was retained when one of the herbivores (C. dubia) was present. Ceriodaphnia dubia exhibited weak and non‐selective grazing on the focal algae, leaving the effect of diversity on biomass and variability essentially intact. In contrast, D. pulex exhibited strong and selective grazing in algal polycultures that qualitatively altered both diversity–function relationships. As algal richness increased, total algal biomass decreased and variation through time increased. These changes were coupled with larger and less variable populations of D. pulex. Our results show that herbivory leads to a richer array of diversity–function relationships than often observed in studies focused on just one trophic level, and suggests trophic interactions should be given more attention in work that seeks to determine how biodiversity impacts the functioning of ecosystems.

Modeling population dynamics and small-scale fisheries yields of fish farming escapes in Mediterranean coastal areas

Coastal ecosystems put up a number of impacts from human activities in the sea; the most recent is fish farming, interacting synergistically with the other impacts and with the natural structure and dynamics of the coastal ecosystem. In the Mediterranean Sea, the number of fish farms has increased dramatically from early ‘80s in coastal waters, releasing a substantial amount of organic matter, modifying the habitat and communities beneath cages and changing the spatio-temporal distribution of species. Among all the effects derived from fish farming, escape events of cultured fish are a relevant issue for management given their potential impact over wild counterparts in terms of habitat and food competition, genetic flow, biodiversity, spread diseases or parasites, and interaction with local fisheries, decreasing the price of the catches. This paper shows the first approach to model the temporal trends of biomass and yields of escapes from aquaculture by means of an EwE model. Three levels of escapes (×1, ordinary level: 5000indyear−1fishfarm−1, corresponding to 1.31tyear−1; massive event: ordinary level×91; total destruction of fish farm: ordinary level×1800) and four levels of fishing effort (ordinary E, ×2, ×5, ×10) were modelled as mechanism to recapture escapees. Temporal variation of biomass and yield is used to define how long should be maintained the effort to catch escapees. The total destruction of a fish farm generates the higher increase of escapees' landings, dissapearing in less than 6 months if fishing effort reach 10-fold the ordinary fishing effort. Differences among revenues from recaptures and derived expenses were always negative but tending to be greater for low levels of fishing effort and/or levels of escapes which means no fishery can be expected to be maintained by escapes. In general, fleets benefit from escapees in terms of yield but gains will depend on how escapees affect either positively or negatively the value of the catch. Simulations using EwE models may result a useful tool to design suitable recapture plans of escapees.

Temporal variations in biomass and size of seabob shrimp Xiphopenaeus kroyeri (Heller, 1862) (Decapoda: Penaeoidea) on the southern coast of São Paulo state, Brazil

Abstract Xiphopenaeus kroyeri (Heller, 1862) is the third most common species caught by fishing boats in the state of Sao Paulo, Brazil and production of this shrimp in the Cananeia region located on the southern coast of this state ranks second in the nation. The aim of this study was to investigate the temporal variation of the total biomass and size of X. kroyeri and analyze this variation against environmental factors in order to suggest some information about the best periods to fish this species. Samples were caught monthly from four sampling stations in Cananeia between July 2012 and June 2014 using a fishing boat equipped with otter-trawl nets. Temperature and salinity were monitored using a multiparameter probe, and sediment samples were also taken using a Van Veen-type gripper for particle size analysis. The shrimp were weighed, quantified, and carapace length was measured (mm). In general, the highest total biomass values were recorded when the fishery was closed in the southeast and south regions, and the highest catch of smaller individuals was also observed during this period. In contrast, in November 2013 the fishing is permitted and high biomass composed of large individuals was observed. The monthly biomass showed a positive relationship with sediment texture, because this species prefers very fine sediments to burrow as a defense against predators.

Biomasse et stocks de carbone des forêts tropicales africaines (synthèse bibliographique)

Introduction. Quantifier les stocks de biomasse et de carbone contenus dans les forêts tropicales est devenu une priorité internationale dans le cadre de la mise en œuvre du mécanisme REDD+. La biomasse forestière est estimée à trois échelles spatiales successives : l’arbre, le peuplement et la région. Cet article propose une synthèse des connaissances sur l’estimation de la biomasse et des stocks de carbone contenus dans les forêts tropicales africaines. Littérature. Cette synthèse bibliographique démontre que peu d’équations allométriques, équations qui permettent d’estimer la biomasse de l’arbre à partir de mesures non destructives (diamètre, hauteur), ont été établies pour les forêts tropicales africaines. Au niveau du peuplement, cette synthèse met en exergue les variations spatiales et temporelles connues de la biomasse entre les types de forêts d’Afrique tropicale. Si la reconstitution de la biomasse après une perturbation (l’exploitation forestière, par exemple) est relativement rapide, il existe encore beaucoup d’incertitudes sur les variations spatiales de la biomasse et il n’y a pas de consensus sur une cartographie régionale de la biomasse. La qualité de la cartographie de la biomasse dépend fortement des différents capteurs utilisés (optique, RADAR ou LiDAR) et de l’équation allométrique utilisée pour convertir les données d’inventaires forestiers en biomasse. Conclusions. Considérant le manque de précision des équations allométriques disponibles et des données d’inventaires forestiers à large échelle spatiale, il y a encore beaucoup d’incertitudes sur les estimations de la biomasse et des stocks de carbone contenus dans les forêts tropicales africaines.

DINÁMICA ESPACIAL Y TEMPORAL DE LA BIOMASA ALGAL ASOCIADA A LAS RAÍCES DE MANGLE EN LA BAHÍA DE BUENAVENTURA, COSTA PACÍFICA DE COLOMBIA

The spatial and temporal variation of biomass of mangroveassociated macroalgae growing on roots of Rhizophora. mangle and pneumatophores of Avicennia. germinans were studied at three sampling stations in Buenaventura bay, Colombia, between November 1999 and September 2003. Eighteen species of algae were collected including nine Rhodophyceae, five Chlorophyceae and four Cyanophyta (Cyanobacteria). Four species dominated the algal flora and collectively contributed with 90 % of the total algal biomass. Bostrychia calliptera was the most dominant with 32 % of the total biomass, followed by Boodleopsis verticillata (26 %), Catenella impudica (18 %), and Caloglossa leprieurii (12 %). Algal biomass between seasons showed significant differences, with higher biomass found during the dry season compared to those of the rainy season. The algal biomass at the mouth of the estuary was significantly higher than that found in the inner areas of the estuary (annual means of 30.7 ± 10.8 vs. 13.8 ± 4.1 g m-2 respectively).Three well-defined vertical zones were observed, based on algal biomass: A narrow upper zone, dominated by B. calliptera; a wide middle zone, with mixed populations of C. impudica and B. calliptera, registering annual mean of 86.8 ± 24.1 g m-2, and a bottom zone, dominated by C. leprieurii and B. verticillata. The results indicated that water level inundation and the vertical position along the roots seem to be the most important factors influencing the algal biomass.

Testing assumptions for conservation of migratory shorebirds and coastal managed wetlands

Managed wetlands provide critical foraging and roosting habitats for shorebirds during migration; therefore, ensuring their availability is a priority action in shorebird conservation plans. Contemporary shorebird conservation plans rely on a number of assumptions about shorebird prey resources and migratory behavior to determine stopover habitat requirements. For example, the US Shorebird Conservation Plan for the Southeast-Caribbean region assumes that average benthic invertebrate biomass in foraging habitats is 2.4 g dry mass m−2 and that the dominant prey item of shorebirds in the region is Chironomid larvae. For effective conservation and management, it is important to test working assumptions and update predictive models that are used to estimate habitat requirements. We surveyed migratory shorebirds and sampled the benthic invertebrate community in coastal managed wetlands of South Carolina. We sampled invertebrates at three points in time representing early, middle, and late stages of spring migration, and concurrently surveyed shorebird stopover populations at approximately 7-day intervals throughout migration. We used analysis of variance by ranks to test for temporal variation in invertebrate biomass and density, and we used a model based approach (linear mixed model and Monte Carlo simulation) to estimate mean biomass and density. There was little evidence of a temporal variation in biomass or density during the course of spring shorebird migration, suggesting that shorebirds did not deplete invertebrate prey resources at our site. Estimated biomass was 1.47 g dry mass m−2 (95 % credible interval 0.13–3.55), approximately 39 % lower than values used in the regional shorebird conservation plan. An additional 4728 ha (a 63 % increase) would be required if habitat objectives were derived from biomass levels observed in our study. Polychaetes, especially Laeonereis culveri (2569 individuals m−2), were the most abundant prey in foraging habitats at our site. Polychaetes have lower caloric content than levels assumed in the regional plan; when lower caloric content and lower biomass levels are used to determine habitat objectives, an additional 6395 ha would be required (86 % increase). Shorebird conservation and management plans would benefit from considering the uncertainty in parameters used to derive habitat objectives, especially biomass and caloric content of prey resources. Iterative testing of models that are specific to the planning region will provide rapid advances for management and conservation of migratory shorebirds and coastal managed wetlands.

Soft sediment macroalgae in two New Zealand harbours: Biomass, diversity and community composition

Macroalgae play key roles in coastal soft sediment environments, acting as primary producers, habitat structure, coastal filters and influencing water movement and sedimentation. Their contribution to biomass and productivity may vary significantly over space and time. Very little research has been carried out on soft sediment algal communities in New Zealand. In this study we documented macroalgal richness, biomass and community composition, comparing sites in Whangarei and Otago Harbours, at two sampling times, and two tidal levels using two collecting methods. We also investigated the contribution of phyla and growth forms to biomass and species diversity. Algal biomass and diversity did not vary significantly between harbours, but did between sites, and temporal variation in biomass was significant. Community composition varied significantly between harbours, times and sites, and was influenced by fetch (a proxy for exposure) and distance to harbour mouth (potentially a proxy for sedimentation or salinity). The contribution of each phylum to biomass was variable, but the Chlorophyta (primarily Ulva and Codium spp.) made a larger contribution in Otago Harbour. Numerically, red algae (Rhodophyta) were dominant in both harbours. Variation in growth forms between harbour, site and time revealed no clear patterns and there were no significant correlations with substrate. The two collecting methods resulted in similar numbers of taxa (161 and 156 respectively), but each method collected ∼30% taxa unique to that method, indicating that they are complementary when used to assess diversity. Our results show that soft sediment environments can offer an unexpectedly high diversity of macroalgal taxa (209 taxa), that areas with low algal biomass can harbour a high diversity of taxa, and, that macroalgal communities appear highly variable in both space (within and between harbours) and time.

Seasonality of eelgrass biomass across gradients in temperature and latitude

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 506:71-85 (2014) - DOI: https://doi.org/10.3354/meps10800 Seasonality of eelgrass biomass across gradients in temperature and latitude Kevin Kuhlmann Clausen1,2,*, Dorte Krause-Jensen2,3, Birgit Olesen4, Nuria Marbà5 1Department of Bioscience, Aarhus University, Grenåvej 14, 8410 Rønde, Denmark 2Arctic Research Centre, Aarhus University, C.F. Møllers Allé 8, 8000 Aarhus C, Denmark 3Department of Bioscience, Aarhus University, Vejlsøvej 25, 8600 Silkeborg, Denmark 4Department of Bioscience, Aarhus University, Ole Worms Allé 1, Building 1135, 8000 Aarhus C, Denmark 5Department of Global Change Research, IMEDEA (CSIC-UIB), Institut Mediterrani d’Estudis Avançats, Miquel Marquès 21, 07190 Esporles, Illes Balears, Spain *Corresponding author: kc@dmu.dk ABSTRACT: Eelgrass Zostera marina L. meadows are major structural and trophic components of coastal ecosystems. The role of eelgrass in ecosystem functioning depends on biomass and production of the meadows, which can fluctuate greatly during an annual cycle and be major temporal drivers of changes in the coastal zone. We analysed magnitude and seasonality of eelgrass aboveground biomass, shoot density and production across temperature and latitude gradients over the majority of the species’ distributional range, and investigated to what extent temperature and/or light drive differences in these values. Eelgrass phenology (timing of peak biomass, start and end of the growing season) showed strong effects of temperature and latitude, indicating that seasonality was considerably advanced in warm areas at low latitudes compared to cold areas at high latitudes. Magnitude of peak aboveground biomass, length of the growing season, mean annual shoot density and aboveground production did not change significantly with either temperature or latitude, indicating that these parameters were controlled mainly by other factors. Annual variation in aboveground biomass and shoot density was significantly smaller in areas with low summer temperature, indicating that while warm-water populations may show substantial temporal variation in biomass, cold-water meadows are less dynamic. These findings were supported by cold-water populations having a larger mean annual biomass and a greater investment in belowground parts. In all significant regressions, temperature was a better predictor of population dynamics than latitude. This indicates that eelgrass phenology might advance considerably in response to global warming, and suggests that the distributional range of this species might be moving northwards. Given the key role of eelgrass in coastal ecosystems, these climate-induced changes might entail substantial impacts on waterbirds, fish, invertebrates and other organisms exploiting these meadows. KEY WORDS: Zostera marina · Climate change · Phenology · Waterbirds · Ecosystem functioning Full text in pdf format PreviousNextCite this article as: Clausen KK, Krause-Jensen D, Olesen B, Marbà N (2014) Seasonality of eelgrass biomass across gradients in temperature and latitude. Mar Ecol Prog Ser 506:71-85. https://doi.org/10.3354/meps10800 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 506. Online publication date: June 23, 2014 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2014 Inter-Research.

Temporal variation of biomass and productivity of Thalassia testudinum (Hydrocharitaceae) in Venezuela, Southern Caribbean

Annual biomass and productivity of Thalassia testudinum were determined during a year at a seagrass bed located in the Parque Nacional Morrocoy, Venezuela. Leaf, rhizome and root biomass were determined monthly, together with short-shoot density, from February 1992 to January 1993, from nine replicated core samples. Productivity was measured using the methodology by Zieman (1974) with minor modifications, and leaf turnover rate was calculated. Leaf biomass values ranged between 101.73 dry g m(-2) in February and 178.11 dry g m(-2) in August. Productivity ranged from 1.69 dry g m(-2) d(-1) in April and October to 3.30 dry g m(-2) d(-1) in July, showing two annual peaks: one in July and one in March. The leaf turnover rate showed the highest value in June (2.41% d(-1)) and the lowest in May (1.23% d(-1)). Sampling time differences in leaf biomass, productivity and turnover rate were statistically significant. Short-shoot density values varied between 811.10 shoots m(-2) in April and 1226.08 shoots m(-2) in December, but the differences were not significant along the year. These results indicated seasonal trends for leaf biomass, productivity and turnover rate of T. testudinum in the Southern Caribbean (latitude 10 degrees N).

Stream inflow and predation risk affect littoral habitat selection by benthic fish

Summary1. We examined small, fishless headwater streams to determine whether transport of macroinvertebrates into the littoral zone of an oligotrophic lake augmented food availability for Cottus asper, an abundant predatory fish in our study system. We sampled fish and macroinvertebrates during the recruitment and growth season of 2 years, either monthly (2004) or bi‐monthly (2005), to observe whether stream inputs increased prey availability and whether variation in total macroinvertebrate biomass was tracked by fish.2. Observations from eight headwater streams indicated that streams did not increase the total macroinvertebrate biomass in the shallow littoral zone at stream inflows, relative to adjacent plots without stream inputs (controls). The taxonomic composition of stream macroinvertebrates drifting toward the lake differed from that in the littoral lake benthos itself, although there was no evidence of any species change in the composition of the littoral benthos brought about by stream inputs.3. Although streams made no measurable contribution to the biomass or taxonomic composition of the littoral macroinvertebrate benthos, there was substantial temporal variation in biomass among the eight sites for each of the (n = 7) sample periods during which observations were made. Variation in total biomass was primarily a function of bottom slope and benthic substrata in the lake habitats. Dominant taxonomic groups were Baetidae, Ephemerellidae (two genera), Leptophlebiidae, Chironomidae (three subfamilies) and Perlodidae, although we did not determine the specific substratum affinities of each taxon.4. Mixed effects linear models identified a significant interaction between macroinvertebrate biomass and plot type (stream inflow vs. control) associated with fish abundance. Across the observed range of macroinvertebrate biomass, fish showed a significant preference for stream inflows, but more closely tracked food availability in the controls. For young‐of‐the‐year (YOY), a negative effect of temperature was also included in the model, and we observed lower temperatures at stream inflows. However, abundance of predatory adults affected habitat selection for YOY. Lake‐bottom slope also accounted for variation in abundance in both fish models.5. Our results suggest that the effect of fishless headwater streams on downstream fish may not always be through direct delivery of food. In this study system, fish preferred stream inflow plots, but this preference interacted with macroinvertebrate biomass in a manner that was difficult to explain. For YOY, predation risk was related to the preference for stream inflows, although the specific factor that mitigates predation risk remains poorly understood.

Temporal variations of biomass, carbon and nitrogen of roots under different tree species

Seasonal changes of root biomass, concentrations and masses of carbon and nitrogen in roots and root diameter classes (<2mm, 2–5mm and>5mm) were evaluated under four adjacent coniferous plantation sites: Oriental spruce (Picea orientalis L.), Austrian pine (Pinus nigra Arnold), Turkish fir (Abies bornmulleriana L.), Scots pine (Pinus sylvestris L.) and natural Sessile oak (Quercus petraea L.) forest. The root biomass, carbon and nitrogen concentrations, carbon and nitrogen masses, C/N ratio of roots were evaluated with regards to species, root diameter classes and seasons. The significantly (p<0.05) lowest annual mean root biomass was 258 g/m2 in Austrian pine compared with tree species. The fine root class has significantly the lowest carbon content, with the 42% value, among other root diameter classes. However, the temporal variations of root C (%) presented no statistical significance. The annual mean nitrogen concentrations ranged from 0.56% (Turkish fir) to 0.74% (Austrian pine) among species. We also found that root nitrogen concentrations in January were significantly different from those of other sampling times. C/N ratios showed statistically significant differences in root diameter classes that the ratios were found, 49 for fine roots, 111 for small roots and 143 for coarse roots, respectively.

Spatial and temporal variation in biomass and size structure of Corbicula fluminea in Danube River catchment, Hungary

AbstractThe aim of this study was to reveal the spatial and temporal variation in biomass, density, and size structure of the invasive clam, Corbicula fluminea in the Danube River catchment and to explore the environmental factors determining these patterns. Samples were taken seasonally during the years 2007 and 2008 at 15 sites located along a river continuum from a second order stream to the Danube River. C. fluminea was the most abundant species in the main arm of the Danube; however, it was found in great density in the side arms, too. In the Ipoly River it only occured close to the conjuction, and it was not present at all in the second and third order streams. Regression models were developed to predict dry mass (DW, g) from linear body dimension [shell length (L), mm]. For the description of length-dry mass relationship, the power function (DW = a * Lb) was applied. The highest density, biomass, and mean shell length were 178 ind. m−2, 24.9697 g DW m−2, and 21.99 mm, respectively. ANOVA detected significant spatial variation in biomass; however, significant temporal variation was not recorded between the years, only among the seasons. Multiple linear regressions were used to find the relationship between the biomass and the environmental parameters. The coarse and very fine sediment fractions and the high water temperature provided suitable habitat for C. fluminea. Although statistically significant correlation was not detected between the chlorophyll-a content of water and the biomass, the highest biomass values were recorded at sites with high chlorophyll-a value.

Aquatic prey switching and urban foraging by the White Ibis Eudocimus albus are determined by wetland hydrological conditions

Prey availability is known to limit reproduction of some species of nesting birds, but identifying the primary prey types of a species with a flexible diet can be challenging. For the White Ibis Eudocimus albus, a tactile feeding, medium‐sized wading bird, nestling prey composition is suggested to depend on landscape water depths/availability of foraging habitat at the time of nesting and on historical drying events affecting prey production. We collected and compared inter‐ and intra‐annual diet variation of White Ibis chicks reared in the Everglades over two years that were independently identified as being relatively good (2006) and poor (2007) nesting seasons. We collected 127 nestling boluses and analysed the temporal variation in biomass of eight functional prey groups using multivariate techniques. The boluses from 2006 in the central Everglades were dominated by fish, but in 2007, after fish had been reduced by the previous year of drying, the boluses from the same region were more variable and dominated by garbage (i.e. scavenging). Analysis of five different collections taken from a different colony in the northern Everglades indicated that boluses were characterized by crayfish and had fewer fish or less garbage when landscape water depths were relatively higher and more preferred habitat was available. At lower landscape water depths in 2007 the bolus composition shifted away from crayfish towards small fish and urban food (terrestrial insects and garbage). Our results support the suggestion of depth‐dependent diets; prey composition depends on the current landscape water levels around the colonies, and also suggests that previous drying events can lead to increased reliance on alternative food sources. White Ibis partially compensated for unavailable aquatic prey with alternative urban foods, but their nesting success appears to have suffered.