Studies on habitat selection by amphipods using artificial substrates within an estuarine environment

Field studies on habitat selection and community development of four gammarid amphipod species were conducted in a brackish lagoon at Nanakita River Estuary, Japan. Development of amphipod community was studied by focussing mainly on provision of shelter for these invertebrates. Seven artificial substrates (including wire net cage, circular concrete block, dried oyster shell, brush, sponge, blue and green tapes) were used in the field as substitutes of natural substrates (macroalgae). This paper demonstrates that amphipods will mostly select and inhabit substrates with available space that provide them with adequate protection. Brush substrate was ranked the best among the selected substrates, because its filamentous nature like natural substrates (macroalgae) provided suitable habitat for both tube-dwelling and free-living amphipods and accommodated maximum densities of amphipods in all seasons at all stations. Tube-dwelling amphipods (domicolous) constructed their tubes in and on algal substrates and their densities tended to be correlated with algal biomass, whilst free-living species (nestlers) prowled on surfaces, clang to filamentous structures and hid themselves in crevices, holes and boulders. Brush substrates at different stations suggested the importance of site difference.     

Mechanisms Influencing the Spread of a Native Marine Alga

Like invasive macrophytes, some native macrophytes are spreading rapidly with consequences for community structure. There is evidence that the native alga Caulerpa filiformis is spreading along intertidal rocky shores in New South Wales, Australia, seemingly at the expense of native Sargassum spp. We experimentally investigated the role physical disturbance plays in the spread of C. filiformis and its possible consequences for Sargassum spp. Cleared patches within beds of C. filiformis (Caulerpa habitat) or Sargassum spp. (Sargassum habitat) at multiple sites showed that C. filiformis had significantly higher recruitment (via propagules) into its own habitat. The recruitment of Sargassum spp. to Caulerpa habitat was rare, possibly due in part to sediment accretion within Caulerpa habitat. Diversity of newly recruited epibiotic assemblages within Caulerpa habitat was significantly less than in Sargassum habitat. In addition, more C. filiformis than Sargassum spp. recruited to Sargassum habitat at some sites. On common boundaries between these two macroalgae, the vegetative growth of adjacent C. filiformis into cleared patches was significantly higher than for adjacent Sargassum spp. In both experiments, results were largely independent of the size of disturbance (clearing). Lastly, we used PAM fluorometry to show that the photosynthetic condition of Sargassum spp. fronds adjacent to C. filiformis was generally suppressed relative to those distant from C. filiformis. Thus, physical disturbance, combined with invasive traits (e.g. high levels of recruitment and vegetative growth) most likely facilitate the spread of C. filiformis, with the ramifications being lower epibiotic diversity and possibly reduced photosynthetic condition of co-occurring native macrophytes.     

西湖湖西浮游与着生藻类季节变化及相互关系

2014年11月至2015年8月调查了西湖湖西沿岸带浮游藻类和不同基质(植物、石块和底泥)上着生藻类的群落结构及季节变化, 分析了着生丝状藻与浮游丝状藻的相互关系以及它们与环境因子的相关性, 探讨湖西生态修复过程中季节性暴发的丝状藻水华的原因。结果表明浮游藻类和植物、底泥、石头上着生藻类中均以硅藻门种类数(分别占52.5%、60.4%、86.7%和72.7%)最多, 蓝藻门(分别占10.1%、8.9%、6.7%和15.2%)和绿藻门(分别占26.3%、19.8%、5.6%和10.6%)次之, 其他门类相对较少, 浮游藻类与着生藻类优势种季节差异较大。附植丝状藻密度显著高于附泥和附石丝状藻, 且狐尾藻上着生丝状藻密度与浮游丝状藻密度呈显著正相关, 表明狐尾藻着生丝状藻可能是浮游丝状藻较重要的来源之一, 该结果可为西湖丝状藻水华的控制提供一些参考。相关性分析表明, 着生藻类和丝状藻与各理化因子(水深、透明度、溶解氧、水温、pH、TN、SRP、TP等)均无显著相关性。     

Microhabitat use by a post-settlement stage estuarine fish: evidence from relative abundance and predation among habitats

Seagrass beds provide food and shelter for many fish species. However, the manner in which fishes use seagrass bed habitats often varies with life stage. Juvenile fishes can be especially dependent on seagrass beds because seagrass and associated habitats (drift macroalgae) may provide an effective tradeoff between shelter from predation and availability of prey. This study addressed aspects of habitat use by post-settlement pinfish, Lagodon rhomboides (Linneaus), an abundant and trophically important species in seagrass beds in the western North Atlantic and Gulf of Mexico. Abundance of post-settlement fish in seagrass beds was positively related to volume of drift macroalgae, but not to percent cover of seagrass, indicating a possible shelter advantage of the spatially complex algae. Tethering experiments indicated higher rates of predation in seagrass without drift macroalgae than in seagrass with drift macroalgae. Aquarium experiments showed lower predation with higher habitat complexity, but differences were only significant for the most extreme cases (unvegetated bottom, highest macrophyte cover). Levels of dissolved oxygen did not differ between vegetated and unvegetated habitats, indicating no physiological advantage for any habitat. Seagrass beds with drift macroalgae provide the most advantageous tradeoff between foraging and protection from predation for post-settlement L. rhomboides. The complex three-dimensional shelter of drift macroalgae provides an effective shelter that is embedded in the foraging habitat provided by seagrass. Drift macroalgae in seagrass beds is a beneficial habitat for post-settlement L. rhomboides by reducing the risk of predation, and by providing post-settlement habitat within the mosaic (seagrass beds) of adult habitat, thus reducing risks associated with ontogenetic habitat shifts.     

Habitat structure,resources and diversity: the separate effects of surface roughness and macroalgae on stream invertebrates

Habitat structure has pervasive effects on community composition and diversity, with physically complex habitats often containing more species than physically simple ones. What factors or mechanism drive this pattern is little understood, but a complicating problem is that different sources of habitat structure can be confounded in both surveys and experiments. In this study, we carried out an experiment in which two sources of habitat structure, attached macroalgae and substrate surface texture, were separately manipulated to discern their joint and separate effects upon the diversity and composition of colonizing macroinvertebrates in a stony, upland stream. Because stream algae vary markedly in abundance in both space and time, we also sampled the epilithon of stream stones at two spatial scales on eight dates over 2 years to gain some preliminary data on how stream algae vary between individual substrata over time. Experimental substrata had either a smooth (siltstones, sandstones, crystal-poor felsic volcanics, plain paving bricks) or rough (granodiorites, crystal-rich felsic volcanics, sand-blasted paving bricks) surface. We allowed these substrata to be colonized naturally by macroalgae, mostly the filamentous red alga Audouinella hermannii. Half of each of the rough and smooth substrata were selected at random and the macroalgae gently sheared off. All substrata were defaunated with a household insecticide with little field persistence, set out randomly through the study riffle, and invertebrates allowed to colonize them for 14 days. Some substrata were sampled immediately to check the efficacy of faunal and algal removals, which proved to be successful. Experimental results showed that both surface texture and macroalgae increase species richness independently of each other. Surface texture had no effect on densities, while macroalgae increased colonization densities, but rarefaction showed that both sources of habitat structure increased species richness above values expected simply on the basis of the numbers of colonists. However, reference stones with high macroalgal cover had the same species richness as those with low cover, suggesting that the effects of macroalgae on species richness are transient relative to those associated with surface texture. Epilithon samples taken at different times suggest that the magnitude of spatial variation in plant growth alters with time. If plants generally recolonize rough surfaces more quickly than smooth, then the effects of habitat structure on macroinvertebrates ought to be strongest after major disturbances during growing seasons of plants. Received: 1 September 1999 / Accepted: 10 January 2000     

IMPACTS OF MESOGRAZERS ON EPIPHYTE AND ENDOPHYTE GROWTH ASSOCIATED WITH CHEMICALLY DEFENDED MACROALGE FROM THE WESTERN ANTARCTIC PENINSULA: A MESOCOSM EXPERIMENT1

It has been hypothesized that the extensive mesograzer community along the western Antarctic Peninsula regulates epiphytic algae as well as emergent filaments from endophytic species. Should grazing limit growth of fouling or potentially pathogenic microphytes, then Antarctic macrophytes may actually benefit from the remarkably high densities of mesograzer amphipods that occur in these waters. Although initially counterintuitive, the negative impacts of epi/endophyte fouling may outweigh stresses caused by limited amphipod grazing on chemically defended macrophytes by reducing stress from endo/epiphyte biomass. If so, then alleviating mesograzing stress should result in significant increases in endo/epiphytic biomass. To test this hypothesis, a mesocosm experiment was conducted. Individuals representing four common species of Antarctic macroalgae were placed in flow‐through seawater mesocosms. Amphipods were added to five mesocosms at simulated natural densities, while the other five remained herbivore free. At the end of 7 weeks, endo/epiphytic growth on individual macrophytes was quantified. Most species of macroalgae demonstrated noticeably higher instances of endophyte coverage, epiphytic diversity, and diatom colonization in consumer‐free mesocosms than in the presence of amphipods. These data suggest that macroalgae along the western Antarctic Peninsula rely on grazers to control populations of potentially harmful epiphytes. We hypothesize that the chemically defended macroalgal flora lives in mutualism with high densities of mesograzers, providing amphipods with shelter from predation while continually being cleaned of potentially harmful endo/epiphytes.     

The responses of littoral invertebrates to eutrophication-linked changes in plant communities

The decay of submerged macrophytes in lakes of high trophic level drastically limits the extent of habitat available to littoral invertebrates. The loss can be partially compensated by growth of filamentous algae. Our results show that macroinvertebrates typically associated with submerged macrophytes as well as planktonic crustaceans and rotifers occurred within algal mats at high densities.Aggregations of filamentous algae are usually short-term, with frequent appearances and disappearances. The rate of colonization of algal mats by invertebrates is rapid. In locations with a high degree of water exchange, animals colonize both living and decomposing algal mats at a similar rate, but in sheltered habitats, decomposing filamentous algae are colonized by a smaller number of animals.Comparison was made between the occurrence of invertebrate macrofauna on Chara spp., Potamogeton perfoliatus, P. lucens and Myriophyllum spicatum in several lakes. Although these macrophytes differ visibly in morphology and phenology, the number and composition of macroinvertebrates during summer was associated more closely with trophic state of a lake than with plant species.     

Using macroinvertebrate species assemblages to identify river channel habitat units: an application of the functional habitats concept to a large,unpolluted Italian river (River Ticino,northern Italy)

The functional habitat concept was applied to a large Italian river for the first time. The characteristically wide range of hydraulic conditions present in this river (compared to previously-studied small, lowland, English rivers) were expected to be of central importance to biota and, therefore, to habitat definition. TWINSPAN analysis of the invertebrate assemblages sampled in the Ticino river identified five distinct habitats: two habitats in lotic areas (run-riffle and macrophytes in current), two along the river margins (with and without macrophytes) and one in backwater areas. These correspond to five of the functional habitats identified in U.K. lowland rivers. Each of these five functional habitats could be defined either in terms of hydraulics, substratum and/or presence/absence of macrophytes. Representative taxa are presented for each habitat and community structure discussed. Macrophyte and run-riffle habitats supported the most heterogeneous and abundant benthic fauna. No match was found between replicates grouped by invertebrate assemblage (the five functional habitats identified by TWINSPAN) and the grouping of the same replicates by PCA, carried out on the physical data matrix. While obvious velocity differences were found between the functional habitats, of particular note was the fact that the Froude number did not show any clear association with habitat type. In the future, improved river management will follow improved understanding of river habitats.     

Disproportionate Contribution of Vegetated Habitats to the CH4 and CO2 Budgets of a Boreal Lake

Ecosystems - Many lakes have areas that are colonized by different types of macrophytes, including emergent plants that are rooted in sediments. Emergent macrophytes are known to influence local...     

Long-term changes in amphipod population dynamics in a temperate estuary following ecosystem restoration

The Mondego estuary (Portugal) has suffered severe ecological stress over the last two decades, as manifested in the replacement of seagrasses by opportunistic macroalgae, degradation of water quality and increased turbidity. A restoration plan was implemented in 1998, which aimed to reverse the eutrophication effects, and especially to restore the original natural seagrass (Zostera noltii) community. This article explores the long-term changes in Ampithoe valida and Melita palmata (Amphipoda) populations in response to eutrophication (with consequent seagrass loss and macroalgal proliferation) and to the subsequent restoration plan (with progressive seagrass recovery and macroalgal biomass decline). Until the early 1990s, high densities of A. valida and M. palmata were recorded in the Mondego estuary, especially during the occurrence of the macroalgal bloom and during all the periods in which green macroalgae were available. After the implementation of the restoration plan, species abundance, biomass and production levels decreased considerably due to the progressive decline of green macroalgae. This implied the virtual disappearance of the amphipod population, mainly A. valida. Distinct behaviours displayed by the two species could be related to different food strategies and habitat preferences. Ampithoe valida showed feeding preferences for ephemeral softer, filamentous or bladed algae (e.g. Ulva sp.) due to its high caloric content, using the Z. noltii bed only as a habitat for protection against predators or shelter from wave action. On the other hand, M. palmata did not suffer a strong decline in its population density, biomass and production, which may indicate that this species is probably not a primary consumer of green macroalgae and may readily shift to alternative ecological niches. Handling editor: P. Viaroli     

Substratum selection by juvenile flounder Platichthys flesus (L.): effect of ephemeral filamentous macroalgae

Selection of substrata representing habitats with or without filamentous vegetation by juvenile flounder Platichthys flesus was investigated in laboratory experiments and a field study to assess the effect of the increasing occurrence of ephemeral filamentous macroalgae in shallow nursery areas and its potential effect on flounder recruitment. In the laboratory experiments, 79% of juvenile flounder (24–99 mm total length, L _T) preferred bare sand substrata in comparison to substrata with simulated filamentous vegetation. Substratum preference did not change with fish size. Field sampling using a drop trap (1 m²) in a vegetated (>50% coverage of ephemeral macroalgae) habitat in June, July and August showed small flounder (mean L _T= 37·3 mm) were caught more often in samples with less vegetation. In contrast, larger flounder (mean L _T= 57·2 and 79·7 mm in July and August, respectively) were more evenly distributed in relation to the distribution of vegetation. The results of this study indicate that the increase in ephemeral macroalgae observed in recent years potentially reduces the quantity and quality of suitable nursery habitats for juvenile flounder, which could have detrimental consequences to the overall recruitment of flounder in coastal areas.     

Spatial and Temporal Pattern of Caddisfly Distribution at a Mesohabitat Scale in two Patagonian Mountain Streams Subjected to Pastoral Use

Substrate, flow type, nutrients, aquatic vegetation, organic matter, and caddisfly community structure were studied at two low order streams (Glyn and Nant y Fall) subjected to pastoral use in the Patagonian mountains. At both sites, we examined the effect of habitat type (boulder‐pebble with and without filamentous algae, cobble‐pebble, gravel‐sand, leaf‐pack, the submerged macrophytes Myriophyllum quitense and Isoetes savatieri) and season (high and low water period) on caddisfly assemblages. Benthic particulate organic matter (BPOM) ranged between 4.6 and 472 g m^–2, all allochtonous detrital fractions were significantly higher at leaf‐packs at Glyn, whereas M. quitense habitats supported more BPOM and macrophytes biomass at Nant y Fall. As expected, boulder‐pebble sustained higher Trichoptera richness than M. quitense and gravel‐sand, moreover all habitats showed higher density than M. quitense at Nant y Fall. According to our results at least nine caddisfly species exhibited some habitat preference with boulder‐pebble and cobble‐pebble the most selected habitat. These particular habitats sustained more than 68% of the total caddisfly species. Multidimensional scaling ordination highlighted differences in composition per habitat for both sites showing a clear distinction among depositional and erosional habitats. Substrate, flow type, detritus biomass were important predictors defining assemblages. Based upon our findings, those anthropogenic actions or stressors that change hydraulic as well substrate attributes in mountain streams such as stock trampling, dredging, clearing of riparian areas, will reduce caddisfly richness. These results are relevant for outline management and conservation biomonitoring and schemes in headwater Patagonian streams as well as other similar environments worldwide (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Simulation of hurricane-like disturbances on a Caribbean seagrass bed

We tested the hypothesis that hurricanes cause changes in the plant community structure of Caribbean seagrass beds by acting selectively on populations of rooted macrophytes, which include seagrasses and rhizophytic algae. We also tested the hypothesis that susceptibility to elimination of the rooted macrophytes by the disturbance depends on differences in their growth forms. Two commonly registered disturbances by hurricanes in shallow seagrass beds are burial and sediment removal, which were simulated in marked plots of 1.1 × 1.1 m, at two randomly selected stations in Puerto Morelos tropical reef lagoon. The treatments consisted of control (no disturbance), two levels of burial, and two levels of sediment removal, with four replicates per treatment per station. The experiment was initiated in July 2002 and, 2 months afterwards, the densities of the populations of macrophytes were measured in experimental units of 0.8 × 0.8 m within the plots. MDS analysis showed that both sediment removal and burial caused changes in the species composition of the seagrass community. At one station, burial had a greater impact than sediment removal, whereas at the other station, the degree of impact of both types of disturbance was similar. Some macrophytes were consistently removed more than others, supporting the selective elimination hypothesis. Populations of Thalassia testudinum Banks ex König, Halimeda spp., and spongy algae (Avrainvillea spp. and Cladocephalus spp.) were, in almost all cases, undamaged by experimental manipulations. The populations of Syringodium filiforme Kütz., brush-like algae (Penicillus spp. and Rhipocephalus spp.), and Udotea spp. were reduced by more than 70%, when averaged across all manipulations and stations. A comparative analysis of growth forms of the above-mentioned macrophytes suggested that a solid, deeply anchored root-rhizome or rhizoid system, combined with a flexible or modular above-ground structure, is an advantageous characteristic to resist perturbation by hurricanes or storms.     

Abundance,size, and feeding success of larval shortnose suckers and Lost River suckers from different habitats of the littoral zone of Upper Klamath Lake

We examined near-shore habitat use by larval shortnose and Lost River suckers in the lower Williamson River and Upper Klamath Lake of south-central Oregon. Emergent macrophytes Scirpus, Sparganium and Polygonum supported significantly more, larger, and better-fed larvae than submergent macrophytes, woody vegetation, or open water. Abundance, size, and gut fullness were similar for sucker larvae collected from different emergent macropytes. During the larval period, there was no evidence of density dependant effects or habitat shifts. Ranked catch per unit effort data indicated potential predators also were more likely to use emergent macrophytes, but ordination indicated larvae and potential predators were differentially distributed along a vegetation structure-water depth gradient with larvae in shallow vegetated areas. Between-habitat differences appeared to be due to larval sucker selection for, or better survival in, emergent macrophytes, rather than differential access or exclusion from other habitats. The importance of emergent macrophytes appears to be related to increased foraging success and reduced predation. Because larvae in emergent macrophytes have a size and gut fullness advantage, the amount of emergent habitat could affect early survival. However, interannual differences in recruitment to the adult population may or may not be dependent on larval dynamics. Our results suggest larval sucker access to emergent macrophytes may be necessary, but perhaps not sufficient, for promoting good year class formation.     

Effects of macroalgal identity on epifaunal assemblages: native species versus the invasive species Sargassum muticum

Seaweeds are a refuge from stressful conditions associated with life on rocky intertidal shores, and there is evidence that different macrophytes support different assemblages of mobile epifauna. Introduction of non-indigenous macroalgae may have a great impact on associated epifaunal assemblages and ecosystem processes in coastal areas. Previous studies have reported conflicting evidences for the ability of epifauna to colonize non-indigenous species. Here, we analyzed epifaunal assemblages associated with three species of macroalgae that are very abundant on intertidal shores along the Galician coast: the two native species Bifurcaria bifurcata and Saccorhiza polyschides and the invasive species Sargassum muticum. We collected samples of each species from three different sites at three different times to test whether variability of epifaunal assemblages was consistent over space and time. Epifaunal assemblages differed between the three macroalgae. Results suggested that stability and morphology of habitat played an important role in shaping the structure of epifaunal assemblages. This study also showed that the invasive S. muticum offered a suitable habitat for many invertebrates.     

Microalgal plankton composition in shallow coastal inlets in contrasting trophic and alternative community states

As the trophic state of the environment changes, communities develop into divergent states. These community states are conventionally reflected through primary producers, because they are directly affected by nutrient availability. Studies of submerged macrophytes often focus on community composition to decipher the vegetative (community) state of the environment, while planktic microalgae are usually viewed more cursorily. Although microalgal plankton composition has been related to the trophic state of shallow temperate lakes, corresponding qualitative knowledge is lacking for shallow inlets in the sea. We assessed the composition of microalgal plankton in relation to that of submerged macrophytes in shallow inlets in the northern Baltic Sea during one ice-free season. Microalgal plankton composition varied distinctively among inlets in different trophic and vegetative states especially during early and mid-season, before becoming comparably uniform. These patterns were consisted both inside and outside of macrophyte beds and during day and night. Local and diurnal variation was comparably high in eutrophic and charophyte-dominated inlets, but only during early season. Microalgal plankton composition not only reflects the state of littoral communities in varying trophic conditions, but it may also be important for the whole trophic structure of those communities.     

Seasonal zooplankton dynamics in main channel and backwater habitats of the Upper Mississippi River

This study used stratified random sampling to examine the spatial and temporal distribution of zooplankton communities in a large floodplain river (Mississippi River, USA). Potential mechanisms controlling zooplankton abundance and community structure were considered. Main channel and backwater habitats included in this study differed between a turbid upper pool reach where aquatic macrophytes were sparse and a lower pool reach which was considerably less turbid and had extensive aquatic macrophyte coverage. Samples were collected monthly during the summer over a 2-year period and multivariate analysis was used to examine the spatial and temporal distribution of zooplankton. Significant differences were found in zooplankton density and community composition among habitats and reaches within the pool. Rotifers were the dominant taxa and seasonality was pronounced, with peak densities often occurring in late-spring. Community structure varied by habitat and reach, which suggests that water quality, physical habitat characteristics, presence of aquatic macrophytes, and zooplankton sources can all influence the zooplankton communities of the Upper Mississippi River. Characterization of the zooplankton communities provides a basis for understanding changes in the river ecosystem and examination of zooplankton communities among habitats provides insight into the mechanisms affecting zooplankton dynamics.     

区域变动尺度上不同生境类型及环境因子对西双版纳蝴蝶多样性的影响

【目的】生境类型和环境因子对物种分布和维持具有重要的影响。本研究通过分析不同生境类型对蝴蝶群落多样性及其群落结构影响的差异,以及环境因子对蝴蝶物种丰富度和多度的影响,为区域变动尺度蝴蝶多样性维持机制的研究奠定基础。【方法】于2019年8月和10月,在西双版纳地区采用样线法,调查了天然林、次生林、复合生境、人工林和农田5种生境中蝴蝶的物种,分析了蝴蝶群落多样性、群落结构相似性及物种丰富度和多度与环境因子的关系。【结果】2019年从西双版纳共采集蝴蝶2 226头,隶属于11科98属175种,在西双版纳州级尺度上蝴蝶物种丰富度高于县域尺度。在西双版纳州级尺度上,蝴蝶的物种丰富度和多度在5种生境间存在显著差异,而在县域尺度上,物种丰富度、多度和Chao 1物种丰富度估计值没有一致性规律。群落结构相似性结果显示,在西双版纳州级尺度上,蝴蝶群落结构在不同生境类型间存在极显著差异,在县域尺度上,仅勐腊区域蝴蝶群落结构在不同生境类型间存在显著差异。蝴蝶物种丰富度和多度不仅受到生境类型的影响,还受到温度、年均降水和海拔的影响。【结论】本研究结果表明,在区域变动尺度上,生境类型对西双版纳蝴蝶的多样性的影响较大,而温度、年均降水和海拔是维持蝴蝶物种多样性的重要因素。这些发现对当前人类导致的生境丧失和气候变化时代生物多样性的保护具有重要意义。     

Untangling climate and water chemistry to predict changes in freshwater macrophyte distributions

Forecasting changes in the distributions of macrophytes is essential to understanding how aquatic ecosystems will respond to climate and environmental changes. Previous work in aquatic ecosystems has used climate data at large scales and chemistry data at small scales; the consequence of using these different data types has not been evaluated. This study combines a survey of macrophyte diversity and water chemistry measurements at a large regional scale to demonstrate the feasibility and necessity of including ecological measurements, in addition to climate data, in species distribution models of aquatic macrophytes. A survey of 740 water bodies stratified across 327,000 square kilometers was conducted to document Characeae (green macroalgae) species occurrence and water chemistry data. Chemistry variables and climate data were used separately and in concert to develop species distribution models for ten species across the study area. The impacts of future environmental changes on species distributions were modeled using a range of global climate models (GCMs), representative concentration pathways (RCPs), and pollution scenarios. Models developed with chemistry variables generally gave the most accurate predictions of species distributions when compared with those using climate variables. Calcium and conductivity had the highest total relative contribution to models across all species. Habitat changes were most pronounced in scenarios with increased road salt and deicer influences, with two species predicted to increase in range by >50% and four species predicted to decrease in range by >50%. Species of Characeae have distinct habitat ranges that closely follow spatial patterns of water chemistry. Species distribution models built with climate data alone were insufficient to predict changes in distributions in the study area. The development and implementation of standardized, large‐scale water chemistry databases will aid predictions of habitat changes for aquatic ecosystems.     

The distribution of microcrustacea in the littoral zone of a freshwater lake

The distribution of microcrustacea in the water column, sediments and on different macrophyte species was examined in the littoral zone of Jack Lake, Nova Scotia, Canada. Large numbers of microcrustacea occurred in association with macrophytes, suggesting that this habitat should receive greater attention in future studies of microcrustacean numbers, biomass, and production. The relative abundance of different microcrustacea varied considerably among sediments, macrophytes and water column samples. Although microcrustacean species composition differed among macrophyte groups, consistent differences in absolute numbers per gram could not be demonstrated. Epiphytic microcrustacean community structure also varied among depth strata in Jack Lake. Few epiphytic and benthic microcrustacea migrated into the water column on a diurnal basis.