Colonization by Macroinvertebrates of Experimentally Disturbed Stones in Three Tropical Streams Differing in Size

We experimentally disturbed stones in three streams of different sizes and followed the macroinvertebrate colonization process in terms of abundance, species richness and similarity over 64 days. We hypothesized that colonization in the smallest and in the largest streams would be slower than in the medium‐sized stream. The small upstream pool of colonists available in the smallest stream could restrict colonization, while in the largest stream predation by the diverse fish assemblage could restrict drifting colonists. The medium‐sized stream did not have these two constraints. We found similar colonization patterns in all three streams, leading to the rejection of the stated hypotheses. Lack of support of the original hypothesis might be due to the weakness of the two hypothesized restrictions on colonization. In addition, colonization by crawling species from undisturbed nearby patches might be of significant importance. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Spatio-Temporal Distribution and Ecological Preferences of Coexisting Hydropsychid Species (Trichoptera) in Two Mediterranean River Basins (S Spain)

The hydropsychids of two Mediterranean river basins in southern Spain (Guadaira and Guadalete) were investigated from January 1988 to January 1989. The distribution of hydropsychids along an environmental gradient related to altitude varied depending on species. Two distinct species assemblages were observed. one located in the lower altitude sites (the “downstream assemblage” comprising Hydropsyche pictetorum, Hydropsyche exocellata and Cheumatopsyche lepida) and the other in the upper-most areas (the “upstream assemblage” comprising Hydropsyche punica, Hydropsyche infernalis, Hydropsyche instabilis), which displayed a statistically significant preference for this type of habitat. Finally, H. pictetorum, selected the lowest sites. From a temporal point of view most species displayed a high variability in density dynamics between sites, suggesting a strong plasticity in life-cycle phenology.     

Land Use Influences Niche Size and the Assimilation of Resources by Benthic Macroinvertebrates in Tropical Headwater Streams

It is well recognized that assemblage structure of stream macroinvertebrates changes with alterations in catchment or local land use. Our objective was to understand how the trophic ecology of benthic macroinvertebrate assemblages responds to land use changes in tropical streams. We used the isotope methodology to assess how energy flow and trophic relations among macroinvertebrates were affected in environments affected by different land uses (natural cover, pasture, sugar cane plantation). Macroinvertebrates were sampled and categorized into functional feeding groups, and available trophic resources were sampled and evaluated for the isotopic composition of ¹³C and ¹⁵N along streams located in the Cerrado (neotropical savanna). Streams altered by pasture or sugar cane had wider and more overlapped trophic niches, which corresponded to more generalist feeding habits. In contrast, trophic groups in streams with native vegetation had narrower trophic niches with smaller overlaps, suggesting greater specialization. Pasture sites had greater ranges of resources exploited, indicating higher trophic diversity than sites with natural cover and sugar cane plantation. We conclude that agricultural land uses appears to alter the food base and shift macroinvertebrate assemblages towards more generalist feeding behaviors and greater overlap of the trophic niches.     

Macroinvertebrates: Caspian invaders in the reservoirs and rivers of the Kama River basin

The character of the distribution of Caspian invaders in the Kama River basin and the current state of their development in the Kama water reservoirs were studied. The role of invaders in the structure and functioning of bottom communities is reviewed.     

Cumulative effects assessment for the Northern River Basins Study

The primary objective of the Northern Rivers Basins Study (NRBS)was to advance the understanding of how anthropogenic developments haveimpacted the ecology of the Peace, Athabasca and Slave rivers, Canada.To investigate these multiple stressor impacts, the NRBS used acumulative effects assessment (CEA) based upon a weight of evidenceapproach. This CEA determined the exposure and effects of multiplestressors on these systems and included experimental verification ofcausality and linkage of this understanding to field data. Fish studiesconfirmed that dioxins and furans occur in the food web at low levelsacross the basins; detection frequencies for all2,3,7,8-substituted dioxin/furan congeners (2,3,7,8 TCDD/TCDF)were highest near bleached kraft pulp mills. PCDD/Fs, rather thanPCBs or organochlorine pesticides, were the chemicals of concern forhuman exposure. In addition, the recent decline in concentrations ofdioxins and furans in fish was commensurate with improvements in pulpmill treatment technologies. Throughout the basins, enrichment occurredbelow pulp mill and municipal discharges. Multiple stressor effects ofpulp mill effluent were separated from one another by using experimentsthat demonstrated that the primary impact of the mill effluent wasnutrient enrichment. River state was also greatly influenced byhydrologic impacts. In particularly, the Bennett Dam changed the ecologyof the Peace-Slave river-delta systems more than 1500~km downstream,while climate variability was an important contributing factor for thesedelta impacts. Notable contributions of the NRBS model were thecooperation among governments, aboriginal peoples, non-governmentorganizations, industry and other stakeholders, and the two-waycommunications flow among the scientific community and these groups.NRBS science was also deemed relevant because 16 questions forwarded bystakeholders focused the Study's CEA on specific issues of importancewithin the basin. In summary, the NRBS model of CEA included four keycomponents: (1) communication of stakeholder priorities to producerelevant science questions; (2) pursuit of the best availablescientific understanding of ecosystem impacts by engaginginterdisciplinary science teams; (3) assessment of futureenvironmental condition through monitoring and follow-upinvestigation; and (4) communication of results to managers toproduce appropriate regulatory change. This CEA model combines theseelements with scientific rigor to generate meaningful information tostakeholders while also improving regional assessments of riverbasins.     

Spatial Patchiness of Litter, Nutrients and Macroinvertebrates during Secondary Succession in a Tropical Montane Cloud Forest in Mexico

We test the hypothesis that secondary succession in Tropical Montane Cloud Forest (TMCF) in Mexico is accompanied by an increase in the spatial structuring of litter resources, soil nutrient concentrations and the soil macroinvertebrate community at a within-plot scale (5–25 m). This increased spatial structuring is expected because secondary succession in these forests is associated with an increase in the diversity of trees that dominate the canopy. If each tree species generates a particular soil environment under its canopy, then under a diverse tree community, soil properties will be spatially very heterogeneous. Tree censuses and grid sampling were performed in four successional stages of a secondary chronosequence of TMCF. Variography was used to analyse spatial patterns in continuous variables such as nutrient concentrations, while Spatial Analysis by Distance Indices (SADIE) was applied to determine patchiness in the distribution of soil macroinvertebrate taxa. Secondary succession was found to be accompanied by the predicted increase in the spatial structuring of litter resources and the macroinvertebrate community at the within-plot scale. Spatial patterns in the macroinvertebrate community only became evident for all taxa in the oldest forest (100 years old). Patches with low Ca and Mg concentrations in early successional soils were associated with patches where pine litter was most abundant while those with low P concentrations in late successional stages were associated with patches where oak litter was most abundant. Results suggest that anthropogenic disturbance aboveground promotes a more homogeneous resource environment in the surface soil, which compared to older forests, sustains a less diverse and less spatially structured macroinvertebrate community.     

Macroinvertebrates as bioindicators of water quality in the Mkondoa River,Tanzania, in an agricultural area

The suitability of using macroinvertebrates as bioindicators of stream water quality was tested in the Mkondoa River in an agricultural area at Kilosa, using the rapid bioassessment protocol. The family biotic index (FBI) showed marked variation in water quality along the stream from values ranging from 4.1 to 5.0 in the upstream reaches, indicating good water quality, 5.3 to 5.5 in the mid-reaches and 6.0 to 6.5 in the lower reaches. The water quality index (WQI) indicated that water quality was fair (77 ± 0.98) in the upstream reach of the Mkondoa, marginal (55 ± 0.86) in the midstream reach and poor (33 ± 0.45) in the downstream reach. There were significant relationships between biological oxygen demand and dissolved oxygen and the occurrence of specific taxa, mainly Chironomus and Caenis. Significant changes in macroinvertebrate abundance were mostly related to changes in water quality. As in other parts of the world, macroinvertebrate communities proved to be good biological indicators of water quality and they should be used as bioindicators in long-term monitoring of this river.     

Abiotic factors associated with the occurrence of introduced rainbow trout in the Atsuta River

To infer the distribution pattern of introduced rainbow trout, Oncorhynchus mykiss, we compared abiotic factors among tributaries with and without rainbow trout in the Atsuta River, Hokkaido, Japan. Rainbow trout were present in 10 of the 24 tributaries. Stepwise logistic regression analysis indicated that the occurrence of rainbow trout was more likely in low-gradient tributaries and was negatively correlated with elevation. Our results indicate that the successful establishment of rainbow trout can be predicted using abiotic factors, including elevation and gradient.     

Susceptibility of Tree Seedlings to Biotic and Abiotic Hazards in the Understory of a Moist Tropical Forest in Panama

We evaluated temporal patterns of seedling survival of eight Neotropical tree species generated under multiple abiotic and biotic hazards (vertebrates, disease, litterfall) in the forest understory on Barro Colorado Island, Panama. Seedlings were transplanted at first leaf expansion in low densities along a 6-km transect and damage and mortality were recorded for 1 yr. We also planted and monitored small and large artificial seedlings to estimate physical disturbance regimes. During 0–2 mo after transplant, vertebrate consumers of reserve cotyledons caused high mortality of real seedlings, but little damage to artificial seedlings. On real seedlings after 2 mo, disease became an important agent of mortality, despite a decrease in overall mortality rates. Damage by litterfall remained relatively low during the 1-yr study period. Survival ranks among species showed ontogenetic shifts over time, as species changed susceptibility to the mortality agents. Survival after 2 mo was positively correlated with stem toughness, not because species with tough stems were less likely to receive mechanical damage, but because they survived better after receiving mechanical damage. Within each transplant station, artificial seedlings were not good predictors of litterfall damage experienced by real seedlings. Forest-wide litterfall damage level, however, was similar for both real and artificial seedlings ( ca 10%/yr), a moderate level compared to other tropical forests. In conclusion, species traits including biomechanical traits interact to create complex temporal patterns of first year seedling survival, resulting in ontogenetic shifts that largely reflect changes in the relative importance of vertebrate consumers relative to other hazards.     

Pollution of a Tasmanian River by Mine Effluents. II. Distribution of Macroinvertebrates

The distribution and abundance of macroinvertebrates were studied in the South Esk River, Tasmania; a river subject to cadmium and zinc pollution as a result of mining. The groups most intolerant of cadmium-zinc pollution were the Crustacea, Mollusca and Annelida. Highly tolerant groups included aquatic Hemiptera and Arachnida, and larvae of leptocerid trichopterans. A drop in both species diversity and abundance occurred after floods in winter and was probably due to pulses of cadmium and zinc down the river and also to increased molar action of the unstable substrate.     

Honey Pollen: Using Melissopalynology to Understand Foraging Preferences of Bees in Tropical South India

The aim of the study was to use melissopalynology to delineate the foraging preferences of bees in tropical environs. This was done by comparing pollen spectra obtained from the same hives every three months for three years at four sampling locations (in two sites) within a confined landscape mosaic. If melissopalynology is highly replicable, the spatial variation of the pollen spectrum from the honey samples would be much more than the temporal (inter-annual) variations. In other words, given the three factors, Month, Year and Location, honey pollen from different Locations, in a given Year and Month, would be much less similar than samples from different Years, in a given Location and Month. We then determined how the factors, Month, Year and Location, influenced the pollen influx of honey. The pollen analyses of the 42 honey samples collected during the three years yielded 80 pollen taxa/types: 72 dicotyledonous and 8 monocotyledonous, encompassing 41 botanical families spread into seven life forms namely, trees, shrubs, epiphytes, herbs, climbers, grasses, and sedges. Our results showed that pollen spectra were equally comparable between Locations and between Months and Years; the importance of this result is that it helped to demonstrate the complexity of ecological/environmental phenomena involved in the process of foraging by bees in a heterogeneous and complex landscape.     

北京市白河和潮河流域生态健康评价

选取北京市重要的饮用水源密云水库上游白河和潮河流域,结合北京山区流域生态现状,构建了涵盖水域生境结构、水生生物、生态压力和陆域生态格局与功能、生态压力5大类13项指标的评价指标体系,开展了流域生态健康评价。结果表明白河和潮河流域的健康状态整体处于良好等级,但水生生物和陆域生态格局状况相对较差。14个子流域的健康状况差异并不显著,琉璃河、白河下段、汤河上游的健康状况相对较好,潮河中下段和小汤河的健康状况相对较差。流域内不合理的畜禽养殖、岸边带种植及民俗旅游是导致流域生态健康退化的主要原因,建议加强污染负荷排放的控制和监管涉水活动对水生生境的干扰以改善流域健康状况,并重点关注可指示水生态系统早期退化的生物指数,以实现可持续性和适应性的流域管理,保障密云水库的水生态安全。     

Aquatic Resource Use by Indigenous Australians in Two Tropical River Catchments: the Fitzroy River and Daly River

Indigenous people of northern Australia make extensive use of wild resources as a source of food, in their art and craft, and for medicinal purposes. These resources are part of a socially and culturally significant landscape. Using data collected from household surveys across two catchments in northern Australia, the Daly River, Northern Territory (NT) and the Fitzroy River, Western Australia (WA), we describe indigenous aquatic resource use patterns. The former is a perennial system with extensive vegetated wetlands that can remain inundated for 4?C5?months, while the latter can cease to flow during the winter dry season (May?COctober) and its floods usually last for weeks. Subsistence strategies depend on seasonal availability of a wide array of aquatic species and are attuned to the life histories and movement patterns of key species, such as Long-necked Turtle (Chelodina rugosa) and Magpie Goose (Anseranas semipalmata). Indigenous households harvested resources from different habitats. Our results show a clear progression from use of the main river channel shortly after the wet season to use of billabongs late in the dry season in the Daly River, and a constant reliance on the main river channel and tributaries in the Fitzroy River. Difference in the main species utilised appears strongly related to habitat use, with four of the five most commonly harvested in the Daly catchment being non-fish species associated with billabong habitats. Commonly harvested species from the Fitzroy catchment included small bodied species used as bait and two popular food species, Black Bream (Hephaestus jenkinsi) and Catfish (Neoarius spp.). Results suggest that indigenous subsistence strategies are vulnerable to changes in the natural systems that provide the ??ecosystem goods,?? particularly annual inundation of floodplains that drives productivity and provides habitat for some key species. Water resource developments, such as river regulation and increased abstraction for irrigated agriculture, could adversely affect a highly valued customary component of the indigenous economies of tropical Australia.     

Relationships between the Seasonal Variations of Macroinvertebrates,and Land Uses for Biomonitoring in the Xitiaoxi River Watershed,China

The impacts of differences in watershed land uses, and differences in seasonality on benthic macroinvertebrate communities, were evaluated in 12 stream sites within the Xitiaoxi River watershed, China, from April 2009 to January 2010. The composition of macroinvertebrate community differed significantly among three land use types. Forested sites were characterized by high taxa richness, diversity and the benthic‐index of biotic integrity (B‐IBI), while farmland and urban disturbed stream sites presented contrary patterns. The percentage of urban land use, conductivity, dissolved oxygen, ammonia nitrogen and total phosphorus were the major drivers for the variations. The land use related water quality stress gradients of the four sampling seasons were determined by means of four independent Principal Component Analyses. The responses of macroinvertebrate community metrics, to anthropogenic stressors, were explored using Spearman Rank Correlation analyses. All the selected metrics, including total numbers of taxa, numbers of Ephemeroptera, Plecoptera and Trichoptera taxa, percentage of non‐insect abundance, percentage of scrapers abundance, Pielou’s evenness index, Simpson diversity index, and the Benthic Index of Biotic Integrity were correlated significantly with environmental gradients (PC1) in autumn. In other seasons such correlations were less pronounced. Our results imply that autumn is the optimal time to sample macroinvertebrate communities, and to conduct water quality biomonitoring in this subtropical watershed. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Leaf Litter Decomposition of Three Riparian Tree Species and Associated Macroinvertebrates of Eswathu Oya,a Low Order Tropical Stream in Sri Lanka

Leaf decomposition, an important component of the organic matter dynamics in streams, has been widely examined in temperate regions but much less documented in tropical regions. We report here the first study of leaf decomposition in a Sri Lankan stream. The litterbag technique was used. Coarse (8 mm) and fine (100 µm) litterbags, that included or excluded macroinvertebrates respectively, were used to enclose leaves of three dominant riparian tree species: native Ochlandra stridula (bamboo), and the introduced Alstonia macrophylla and Hevea brasiliensis (rubber). A fourth set of litterbags contained a mixture of these three species. Leaf colonization by macroinvertebrates was highest in the early stages of the decomposition process on Hevea leaves but invertebrate densities declined later. The opposite colonization effect was observed on the native Ochlandra leaves: slow colonization with continuing low densities from the beginning to the end of the process. Decomposition of all three species was significantly faster in the coarse than in the fine mesh bags. Alstonia, which has the softest leaf tissue, was most rapidly decomposed while Ochlandra, with its tough structure, was the slowest. Among the invertebrates, insects were the most important leaf colonizing animals, with Diptera, Coleoptera and Trichoptera the most dominant. The invertebrate variety in the mixed bags was higher than in the single‐species leaf bags, where Chironomidae dominated the colonizing assemblages. This study has shown that toughness, indicated by the ‘specific weight of leaf tissue’, and the quality of the leaves was more important in determining breakdown rates than their origin. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Estimating Species Richness and Modelling Habitat Preferences of Tropical Forest Mammals from Camera Trap Data

Medium-to-large mammals within tropical forests represent a rich and functionally diversified component of this biome; however, they continue to be threatened by hunting and habitat loss. Assessing these communities implies studying species’ richness and composition, and determining a state variable of species abundance in order to infer changes in species distribution and habitat associations. The Tropical Ecology, Assessment and Monitoring (TEAM) network fills a chronic gap in standardized data collection by implementing a systematic monitoring framework of biodiversity, including mammal communities, across several sites. In this study, we used TEAM camera trap data collected in the Udzungwa Mountains of Tanzania, an area of exceptional importance for mammal diversity, to propose an example of a baseline assessment of species’ occupancy. We used 60 camera trap locations and cumulated 1,818 camera days in 2009. Sampling yielded 10,647 images of 26 species of mammals. We estimated that a minimum of 32 species are in fact present, matching available knowledge from other sources. Estimated species richness at camera sites did not vary with a suite of habitat covariates derived from remote sensing, however the detection probability varied with functional guilds, with herbivores being more detectable than other guilds. Species-specific occupancy modelling revealed novel ecological knowledge for the 11 most detected species, highlighting patterns such as ‘montane forest dwellers’, e.g. the endemic Sanje mangabey (Cercocebus sanjei), and ‘lowland forest dwellers’, e.g. suni antelope (Neotragus moschatus). Our results show that the analysis of camera trap data with account for imperfect detection can provide a solid ecological assessment of mammal communities that can be systematically replicated across sites.     

Seasonality of Reproduction in Amazon River Dolphins (Inia geoffrensis) in Three Major River Basins of South America1

Reproduction of Amazon River Dolphins, Inia geoffrensis, is generally reported to be highly seasonal; however, this conclusion is based on studies from only one area of Inia distribution from throughout the Amazon and Orinoco river basins. Our observations of live dolphins from the Orinoco, Amazon, and Mamoré river basins (in Venezuela, Peru and Bolivia, respectively) indicate that reproduction in Inia often occurs year‐round, with seasonal peaks varying according to geographic location. Inia neonates in Peru and Bolivia were seen in all seasons, and were observed most often in falling water (season was defined by relative water level). Conversely, neonates in Venezuela were seen at the end of low water and in rising water, yet were never observed during falling water. Inia mating behavior in Peru was observed in all seasons, while mating was observed only during falling and low water in Bolivia. Our review of the literature from throughout the range of Inia indicates variation in reproductive seasonality, with year‐round reproduction in some areas. Seasonality of peaks in births varied according to study area, and may be more closely associated with local environmental and prey conditions than with taxonomic relatedness, relative seasonal differences in water levels, or broad geographic distribution.