The Plecoptera of Øvre Heimdalsvatn

The stonefly fauna was studied in the exposed zone and on soft bottom in deeper waters. Emergence was recorded by traps. Ten species were found. All were recorded in the exposed zone. Diura bicaudata (L.) and Nemoura avicularis Morton dominated.
During the winter N avicularis occurred in large numbers on soft bottom at nearly all depths while D. bicaudata was only recorded on stony substratum in shallow water. N. avicularis was therefore more susceptible to predation and was recorded in trout stomachs during most of the year, while D. bicaudata was preyed upon only during the short emergence and flight period.
The growth of the most numerous plecopteran species took place partly while the lake was covered by ice. D. bicaudata had two thirds of its growth during this period, while N. avicularis only had one third of its growth during the same period.     

The ecology of Saint Paul's Rocks (Equatorial Atlantic)

St Paul's Rocks are a remote group of islets, barely 400 m across, in the equatorial mid-Atlantic (o°55'N 29°21'W). The results of a primarily zoological survey of the Rocks, carried out in September 1979 by the Cambridge Expedition to Saint Paul's Rocks, are reported. In addition, earlier studies of the Rocks' biology are discussed in the light of recent research. The terrestrial fauna is dominated by three species of sea-bird and a land crab. Also reported from on land are a few species of insects, ticks and spiders, an endemic pseudoscorpion, and a centipede; the majority of these species are associated with the seabirds.
The islets are devoid of tracheophytes, bryophytes and lichens.
The marine ecology of the Rocks is discussed with respect to habitat. Five habitats are distinguished in the supralittoral and littoral zones; the fauna and to a limited extent the flora of each is described. Sublittorally the Rocks consist almost entirely of steep escarpments extending to 60 m depth and beyond. The shallow sublittoral (< 60 m deep) is divided into four habitats: (1) Palythoa zone; (2) Caulerpa zone; (3) sub- Cauferpa zone, and (4) areas of unstable substrates. The Palythoa zone occupies a band extending from the base of the littoral to a depth of c . 5m and is dominated by a mat-forming hexacoral, Palythoa caribaeorum. Below this zone to a depth of c . 33 m the rock faces are thickly invested by a species of green-alga, Caulerpa racemosa. At depth this Caulerpa dominated zone is succeeded by an invertebrate dominated community. Unstable substrates are represented by a few pockets of coarse sand and some patches of rubble. The communities in each of these habitats are described. A primarily taxonomic review of the deep-water fauna is also included. Finally, the influence of ocean currents on the zoogeographical relationships of the Rocks' fauna is briefly examined.     

Ecological studies on crater lakes in West Cameroon. Debundsha Lake

Cape Debundsha receives 10 m (400 inches) of rain per year, and the water of the small crater lake on the cape has one of the lowest conductivities in Africa (11–13 µmho/cm/20 C). The lake has a maximum depth of 13·5 m. At the time of our visit in April 1972 the lake was stratified with a depletion of oxygen in the hypolimnion. The phytoplankton was dominated by Botryococcus , and the zooplankton was dominated by the ostracod Oncocypris debundshae. Both these organisms are closely associated with the surface film. Other zooplankters included Thermocyclops hyalitws , and in deeper water during the daytime the larvae of Chaoborus ceratopogones.
The fauna of the lake includes 12 species of testacean rhizopods, six species of rotifers, two oligochaetes, one snail, seven crustaceans, 15 insects and three acarines. Of the last group two species were new to science and one had been found only once previously. The ectoproct polyzoan, Lophopodella carteri , is recorded for the first time from West Africa, and the second time from Africa. The general impression of the fauna is one of sparseness, with an unusually high proportion of larval Odonata.     

A comparative study of colonization by benthos in a lake and its outflowing stream

1. The patterns of colonization of littoral benthos onto hard substrata on an exposed and a sheltered shore of Lake Purrumbete in Victoria, Australia, and the riffles of its outflow stream (Curdies River) were examined experimentally in winter and summer. The common taxa in the lake (gastropods, amphipods, isopods, planarians, ostracods) also occurred in the stream, although they were not abundant. The stream fauna was dominated by insects. 2. Defaunated half-bricks were sampled at each of three sites at the three different locations (exposed shore, sheltered shore, stream) in winter and summer at weekly or biweekly intervals, with natural stones also being sampled during the colonization period. Colonization patterns of individual taxa which occurred in both the lake and stream, and stream-only taxa, were compared using ANOVA, and the changes in the assemblage through time and between locations were analysed with non-metric multidimensional scaling (NMDS) and analysis of similarities (ANOSIM). 3. Colonization in the lake was very rapid, with species richness and assemblage composition on bricks after just one day matching that of natural stones. Colonization in the stream was slower, the assemblage composition not matching natural stones after 42 days in winter but being comparable after 28 days in summer. There was considerable species turnover during colonization in the stream, but little turnover in the lake, with most common taxa back after one day. There was little difference between the two lake shores in colonization patterns. 4. Taxa that occurred in both lake and stream showed broadly similar patterns of colonization, with early occupancy at high densities. In contrast, stream insects showed a variety of colonization strategies. 5. These results indicate that rates and patterns of colonization on to hard substrata are quite different in Lake Purrumbete compared with its outflowing stream. The rapid colonization in this lake indicates great mobility for much of the fauna on hard substrata, possibly by swimming, benthic crawling or passive drift (even attached to floating vegetation). This may be an appropriate strategy in lake littoral zones where the amount of inhabitable hard substrata and accompanying food resources may be limited.     

Quantitative trends of zebra mussels in Lake Balaton (Hungary) in 2003–2005 at different water levels

During the extremely dry period between 2000 and 2003, the water level of Lake Balaton decreased by 82 cm and 80% of the stony littoral, an important habitat for the zebra mussel (Dreissena polymorpha), became dry. A recovery period started in 2004 due to intense precipitation, which increased water levels in the lake. Seasonal and spatial variations of the relative abundance, population density, population structure and biomass of the zebra mussel and the relative abundance of the amphipod Chelicorophium curvispinum were monitored in the period of 2003–2005 at four different shoreline sections and in two different portions (on the bottom and near the surface portion of the rip-rap) of Lake Balaton. Along with these studies, a quantitative survey of mussel larvae found in the plankton and of the abundance of mussel feeding diving ducks were made. As a consequence of the water level fall, on the dried part of the stony littoral, numerous zebra mussel druses perished. Following the dry period in early 2004, the relative abundance of the mussel on the bottom stones was smaller than in 2003 and the bottom community was dominated by C. curvispinum. By the end of 2004 and during 2005, the water level returned to normal and the surfaces of the reinundated stones were conducive to the successful colonization of zebra mussels. Hence, they returned as the dominant fauna in 2005. The stones near the surface might provide a new substrate for the recruitment of zebra mussels, probably offering more suitable substrata for the settlement in 2005 than in 2003. Therefore, the new substrata available in 2005 may have encouraged better and more rapid zebra mussel colonization than before. Zebra mussels may be better competitors for new space than C. curvispinum. A minor change of water-level fluctuation in 2005 and the reduction in population size of the mussel feeding waterfowl could have contributed to the intensive spread of zebra mussel by 2005.     

Littoral benthos of a Victorian lake and its outlet stream: Spatial and temporal variation

Abstract There have been few comparative studies of the fauna in the two major types of freshwater systems, lakes and streams, in the one locality. This study compared the faunal assemblages at two times of the year (summer and winter) on stones in three locations: the littoral zone of two shores in Lake Purrumbete (one wave-exposed and one sheltered) and riffles in the Curdies River, which flows out of the lake. The lake fauna was dominated by crustaceans, gastropods and planarians, whereas the stream fauna was dominated by insects. The most abundant lake taxa were also present, but much less abundant, in the stream. The total number of species and individuals and densities of some common species varied between the three locations and between seasons. However, no consistent pattern reflecting a difference between the two lake shores was evident. Interpretation of MDS ordinations of the lake fauna was dependent on the data standardizations applied, with increased separation of the season-location combinations when species were standardized to equal total abundances; the seasonal difference was always greatest for the exposed (cliff) shore. In contrast, MDS on the stream fauna showed seasonal differences under all standardizations. This was consistent with the high seasonal turnover of species in the stream compared with the lake. These results demonstrate that, even within a local area with similar geology and connected water bodies, lake and stream fauna from the same substratum (stones) can be markedly different. Taxa that occurred in both were more abundant in the lake, whereas seasonal differences in abundance were much greater in the stream.     

The role of chironomids (Diptera) in the profundal macrozoobenthos in Finnish reservoirs

The proundal macrozoobenthos of 12 Finnish inland polyhumic reservoirs was studied by quantitative sampling in 1984 and 1986. Additionally, the succession of the macrozoobenthos in one young reservoir (Lake Kyrkösjärvi) was studied during its first six years. The zoobenthos material was analyzed using the DCA (detrended correspondence analysis) method, and the ordination of sites (i.e. reservoirs), was related to associated environmental data. The role of chironomids was, in general, important in the profundal of the reservoirs. Because of the coarse bottom quality at many sampling sites, many littoral taxa were found in the profundal zone. The genusChironomus dominated (>50% of the total zoobenthic biomass) especially in the acidic, upper-reach reservoirs.Chironomus larvae also dominated in the zoobenthos of Lake Kyrkösjärvi during its first three years. Some of the reservoirs showed similarities with the dystrophic lake type of the lake typology system (Brundin, 1956). Because of the initially eutrophic character of the bottom, many reservoirs belonged to eutrophic lake types. Finnish reservoirs appear to contain a zoobenthic fauna intermediate between natural lakes and bog pools. This theme was discussed from the ecological and evolutionary point of view ofChironomus species.     

The invertebrate fauna of the streams in Øvre Heimdalen

The lotic communities in Øvre Heimdalen were completely dominated by insects. The species distribution of stoneflies (Plecoptera), mayflies (Ephemeroptera) and caddisflies (Trichoptera) is given together with autecological notes on the Plecoptera and certain other major species. The species distribution of these groups, especially the Plecoptera, was clearly related to the deciduous vegetation along the streams. There was a reduction in species parallel to a reduction in Salix vegetation.
The main inlet stream to the lake, Øvre Heimdalsvatn, the outlet and the outlet stream had different faunal compositions. The inlet fauna consisted to a large extent of winter growing species, mainly detritus feeders, while the outlet and outlet stream had a fauna dominated by summer growing species, several of which were filter feeders.     

Diurnal, horizontal and vertical dispersal of kelp-associated fauna

The kelp Laminaria hyperborea is host for a rich fauna of mobile invertebrates. Dispersal patterns of these animals may be crucial for their availability to visual predators like fish, which are known to search for food in these productive habitats. Diurnal, horizontal and vertical dispersal within and out of the kelp forest were studied by analysing colonization of artificial substrata placed among kelps. The species composition of the fauna was different on three parts of the kelp: lamina, stipes (with epiphytes) and holdfast. The artificial substrata were colonized mainly by species associated with kelp. More species and individuals colonized the artificial substrata at night than during the day. The most abundant faunal groups on the kelps and the artificial substrata were amphipods and gastropods. Both groups dispersed at a significantly higher rate at night than during the day. Rapid horizontal dispersal out of the kelp forest was found. The artificial substrata were also colonized quickly by kelp fauna at all vertical levels inside and above the kelp forest. However, species associated with the kelp holdfast tended to disperse close to the bottom, while stipe-associated fauna moved through all parts of the kelp forest and even above the canopy layer. A high dispersal rate appears common amongst the mobile species living on kelp and seems to be advantageous, despite the risks involved in emigrating from the habitat and being exposed to predators. Higher activity at night may reduce availability to predators.     

Intertidal and subtidal soft-bottom macro- and meiofauna of the Kongsfjord (Spitsbergen)

The intertidal and subtidal soft bottom macro- and meiofauna of a glacier fjord on Spitsbergen was studied after complete ice melt in June 2003. The abundances of the benthic fauna were within the range reported from estuaries and similar intertidal areas of boreal regions. The high proportion of juveniles in the eulittoral zone indicated larval recruitment from subtidal areas. The macrobenthic fauna can be divided into an intertidal and a subtidal community, both being numerically dominated by annelids. Deposit feeders were numerically predominant in intertidal sites, whereas suspension feeders were most abundant in the subtidal area. Among the meiofauna, only the benthic copepods were identified to species, revealing ecological adaptations typical for intertidal species elsewhere.     

On the ecology of littoral Oligochaeta of an oligotrophic Finnish lake

In material sampled from 0.5–6 m on two sampling dates and three subareas the dominant Oligochaeta were Limnodrilus hoffmeisteri Claparède and Peloscolex ferox (Eisen), both composing more than 30% of the abundances of oligochaetes present. The numbers of Oligochaeta were mostly higher in August than in May. Regional differences could be found although the lake seems to be very homogenous. Temporal and vertical variations were detectable in separate subareas. The oligochaete biomass was maximal at 2 m depth. In soft bottom sediments the oligochaetes composed 15.9% of macrobenthos biomass and 12.2% of numbers, but on the stony bottom only 1.9% of numbers. The ratio of Oligochaeta/Chironomidae was similar to those in profundals of oligotrophic lakes. Correlation coefficients between species and two measures of niche overlap were in partial agreement. A temporal niche seems to occur: when the chironomid larvae decrease during the summer, the oligochaetes increase.     

Reactions of some caddis larvae (Trichoptera) to different types of substrate in an experimental stream *

In laboratory experiments with full-grown larvae of three Trichoptera species (Limnephilus rhombicus, Potamophylax rotundipennis and Sericostoma pedemontanum) in an artificial stream, four types of bottom material were provided in combination with various currents. Only L. rhombicus reacted to low current speed (9 cm/sec), moving downstream when a bottom current was present. L. rhombicus and P. rotundipennis showed a distinct preference for pebbles over sand and for coarse pebbles over crushed brick. S. pedemontanum burrowed under pebbles or stones. L. rhombicus showed a distinct tendency to climb onto the dividing gauze or vertical sticks. All three species preferred shaded parts of the experimental stream to the illuminated parts. The results are related to field observations. Limnephilus rhombicus occurs in stagnant and slow-running waters. Potamophylax rotundipennis is restricted to rather fast-running streams with a perpetual flow, while Sericostoma pedemontanum occurs in the same type of stream.     

The benthic macroinvertebrate community in a coastal sand dune lake relative to habitat and changing lake levels

The benthic macroinvertebrate community (BMI) in a freshwater coastal dune lake without a surface outlet was investigated in May and October, 1986. Fifty-three invertebrate taxa were identified from Carter Lake, including three euryhaline crustacean species (Corophium spinicorne, Gnorimosphaeroma oregonensis lutea, and Acanthomysis awatchensis). Corophium spinicorne dominated the BMI communities of the littoral zones and sphaeriid clams dominated the deepwater community.The lake level dropped about 2.5 m between April and October. Based upon this decline, the lake bottom was divided into four major habitats: a sandy temporarily submerged littoral zone (A); a sandy submerged littoral zone (B); and mid-depth zone of mixed mud and sand and the macrophyte, Nitella (C); and a deep zone (D) with soft mud. The average density of BMI was highest in the littoral zones (A and B) in May and in zone B in October (zone A was dry). The lowest density occurred in zone D. In May, BMI biomass was highest in the littoral zones, but the biomass was highest in the mid-depth zone in October. The mid-depth zone in October. The mid-depth zone had the most diverse community.The two most abundant species in the temporarily submerged area, Corophium spinicorne and Juga plicifera, were found in greater numbers deeper in the lake after the water level dropped, suggesting migration by these species in response to changing water levels.     

Distribution and faunal associations of benthic invertebrates at Lake Turkana,Kenya

The benthic environment and fauna of Lake Turkana were studied during 1978–1979 to determine distribution patterns and associations of benthic invertebrates. Lake Turkana is a large, closed-basin, alkaline lake, located in northern Kenya.Detailed environmental information is currently only available for substrate variations throughout Lake Turkana. Water chemistry and other data are currently inadequate to evaluate their effects on the distribution of Lake Turkana benthic invertebrates. Three weak faunal-substrate associations were discovered at Turkana. A littoral, soft bottom association (large standing crop) is dominated by the corixid Micronecta sp. and the ostracod Hemicypris kliei. A littoral, rocky bottom association, also with a large standing crop, is dominated by various gastropods and insects. A profundal, muddy bottom association, with a very small standing crop, is dominated by the ostracods Hemicypris intermedia and Sclerocypris cf. clavularis and several gastropod and chironomid species.     

A note on Lake Goang, an unusual acid lake in Flores, Indonesia

SUMMARY. 1. Lake Goang has a pH of 2.5. Associated with this low pH are high concentrations of sulphate, chloride, iron and aluminium. There are no fish in the lake.
2. A single species of Heterococcales was found in the phytoplankton.
3. The zooplankton consists of one species of rotifer and a stalked species of Vorticella.
4. The shallow water fauna consists of two species of nematodes, at least two larval Diptera, one trichopteran, a zygopteran, a small crab ( Sundatelphusa ) and a cyclopoid copepod ( Paracyclops ).
5. During January an oily slick appears and is deposited as asphalt around the shore of the lake.     

Diet, food resource partitioning and feeding periodicity of two riffle-dwelling fish species in a New Zealand river

The diets and feeding periodicities of two small, riffle-dwelling fish, the torrentfish, Cheimarrichthys fosteri , and the bluegilled bully, Gobiomorphus hubbsi , were investigated in an unstable, braided New Zealand river from May 1985 to April 1986. Aquatic insect larvae dominated diets of all fish and dietary overlap between species was high in 10 of 12 months. Nevertheless, the relative importance of prey items, as assessed by the index of relative importance (IRI), differed between species. Gobiomorphus hubbsi fed almost exclusively on larval Deleatidium (Ephemeroptera), whereas C. fosteri consumed a greater variety of prey items, with Deleatidium and trichopteran, elmid and chironomid larvae numerically dominant. A dietary switch from Deleatidium to chironomid larvae occurred in both species during December 1985, when total and relative abundances of mayfly and other benthic macroinvertebrate larvae were severely reduced by two consecutive floods. A diel sampling programme indicated that the feeding periodicity of the two species differed: C. fosteri was a nocturnal feeder, whereas G. hubbsi exhibited a strong crepuscular peak in feeding activity. Overall, the two fish partition their food resource weakly by consuming prey items in different proportions and sizes and more strongly by utilizing the food resource at different times.     

Differences in growth of perch (Perca fluviatilis L.) in two small forest lakes

Growth patterns and food composition of perch, Perca fluviatilis L., was studied in two small forest lake populations in southern Finland. Size and morphometry of the lakes and physical and chemical properties of water are similar. There is a clear difference in the growth rates of perch between the two lakes. The difference in growth is highly significant in all age groups. In the first lake there is a perch population of 2 000 (1750 ind · ha^–1) adult fishes. In the second lake there is a small population of pike, that keeps the perch population down: 200 adult perch (530 ind · ha^-1). The main food items of perch are crustacean zooplankton, Asellus aquaticus L. and Trichoptera larvae in the first lake and zooplankton, Odonata larvae, Ephemeroptera larvae and Heteroptera in the second.It is concluded that the main reason for the growth difference of studied perch populations is the different population density. There are also differences in species composition of bottom fauna of the lakes, maybe owing to the floating Sphagnum peat moss vegetation in the second lake. This can also affect the growth difference between the two populations of perch.     

Temporal and spatial distribution of chironomid larvae and oligochaetes in two Dutch storage reservoirs

Long-term changes in distribution and taxonomic composition of chironomid larvae and oligochaetes in two water storage reservoirs in The Netherlands were studied. A succession among the chironomid species was observed. In the last 10–15 years chironomid densities varied. Compared with other lakes chironomid densities were high. Densities of chironomids were higher in the littoral zone than in the profundal zone. The opposite was found for oligochaetes. Densities and composition of the chironomid fauna in the two reservoirs were similar.Procladius, Tanytarsus andHarnischia dominated at all depths. However, pupal exuviae samples showed some differences in chironomid taxonomic composition between the two reservoirs. Orthocladiinae, rarely found in bottom samples, abounded in pupal exuviae samples.     

Phenology and bathymetric distribution of the profundal chironomid fauna in Starnberger See (F.R. Germany)

Results of the first long-term investigation of the profundal chironomid fauna of Starnberger See, a prealpine lake are reported. Data are presented on the qualitative and quantitative composition of the chironomid fauna in the profundal of Starnberger See, on the spatial variation, and on the phenology of the dominant species, based on pupal occurrence and the seasonal distribution of larval instars. Twenty-five distinct chironomid taxa could be recorded in the profundal zone. Typical inhabitants of the profundal zone of Starnberger See are the larvae of the genus Micropsectra. The maximum abundance of Micropsectra larvae were found at 60 m with 5644 Ind.m⁻². Abundance, distribution and phenology of the dominant chironomid species are discussed in comparison with other lakes.