Ecological study of the River Lambourn. Report for the period October 1973 to September 1977

The investigations described in this report were carried out to fulfill three distinct but interrelated objectives. In 1973 the Thames Conservancy were making plans for a second stage of their groundwater scheme which would take water from the chalk aquifers in the valley of the Kennet and they wanted basic information on the ecological state of this river and its upper tributaries. Little appeared to be known about limestone streams and a preliminary study of one of the streams in this area was desirable as a basis for planning more detailed studies if these were needed later. At a progress meeting held in March 1976 the problems and opportunities presented by the developing drought conditions were considered. It was concluded that the ecological effects of the exceptionally low natural flows should be studied and that it would be important to assess the ecological impact of the groundwater scheme if it was brought into operation that year. This could only be done on the Lambourn and the Winterbourne and it was decided that considerable effort should be diverted there for this purpose and that the field observations should be extended to cover any recovery period after the end of the drought. To make this possible it was agreed that the studies of invertebrates and detritus on the Kennet should be reduced considerably and that the proposed study of the limestone stream should be abandoned. The revised objectives were as follows: A detailed ecological study of several sites on the Kennet and its tributaries above Kintbury, extending over at least two years and involving observations on wate r weeds , invertebrates, fish, detritus and the trophic relationships within the river community. Quantitativ e and qualitative sampling of water weeds and invertebrates during one year at a number of sites on several chalk streams to determine whether the patterns and relationships found in the Lambourn are also found at the other sites. Observations on the Lambourn at Bagnor were to continue for most of the period to look for long-term fluctuations and to enable these sites to act as controls with which the other sites could be compared. Further detailed studies on the Lambourn and the Winterbourne to assess the impact of low flows, trial pumping and the operation of the groundwater scheme.

The production of algae growing on gravel in a chalk-stream

Epilithic algae, ie that growing on the surface of stones, was studied as part of the work on the energy flow of the chalk-stream ecosystem, by the River Laboratory. The study area was on Bere Stream and 2 neighbouring streams. The algal biomass was estimated from analysis of chlorophyll a. In Bere Stream the peak chlorophyll a cover occurred in April, while in the neighbouring streams, which have considerably lower nutrient levels, there was on peak. Assuming that 2% of a diatoms dry wt is chlorophyll a, then even in mid-April the biomass of epilithic algae amounted to no more than 15 g dry wt m Super(-2) of exposed gravel. Annual production was calculated to be > 15 times greater than biomass. The estimation of net primary production is always difficult for benthic floras and comparisons are especially difficult when different methods are used. But these figures contrast sharply with those for Ranunculus (water crowfoot) which has a ratio of annual production to maximal seasonal biomass of 1:16. The accumulation of algal biomass is apparently being prevented. Some organic matter may be excreted; some algae will be washed off the bed of the stream by current and grazing by herbivorous invertebrates will also tend to prevent algal accumulation.

The ecology of the Gussage, a lined winterbourne

The Gussage, a Dorset winterhourne (intermittent chalk stream), has been used to convey water from a compensation borehole to the River Allen to supplement its flow to meet demand for water. Sections of the Gussage have been lined with chalk, butyl sheeting or polythene sheeting to prevent water loss through the porous bed. The effects of this major environmental modification associated with these abstraction practices in the winterbourne catchments have been studied in the Gussage system since 1973. To compensate for the lack of adequate pre-lining data, comparative studies have been made on 3 small unlined chalk streams of varying flow regimes, ie. the Crichel (a winterbourne), the North Winterbourne and the Tarrant (permanent discharge in the reaches studies). The distribution of macrophytes and invertebrates in winterbournes are compared with that in natural and artificial permanent streams. Statistical analysis showed samples from the winterbourne sites and the unmodified permanent stream sites are quite distinct, despite the fact that no samples were taken from winterbourne sites during the dry phase. This emphasizes the differences between the fauna of an intermittent and a permanent stream and suggests that alteration of the flow regime could be a significant factor. Where flow regime has been altered, as in the Gussage downstream of the borehole, the samples occupy an intermediate position. Within this group of modified sites there is no apparent gross difference between the invertebrates of lined or unlined reaches.

Organic detritus and its role as a food source in chalk streams

This review deals with the variation in populations of invertebrates and the relationships between invertebrate production and detrital food material in chalk streams. The total quantity of detrital material processed by invertebrate consumers is many times greater than the production of these consumers. The amount of detritus ingested each year by chalk stream invertebrates may well be similar to the annual input of autochthonous primary production plus that from allochthonous tree cover.

Acid precipitation and its effects on aquatic systems in the English Lake District

There is no evidence of an increase in the acidity (lower pH or alkalinity) of water-bodies in the Lake District over the last 50 years. Brown trout occur in acid streams and upland tarns where pH is 4.5-5.2 throughout the year. Their occurrence in such waters in Britain and Ireland has been known for most of this century and there is no previous evidence of harmful effects on salmonid fisheries, though numbers of fish are naturally low. However, many benthic invertebrates that are common in hill-streams where pH is above 5.7 do not occur in more acid streams. This phenomenon occurs in the headwaters of several western rivers in Cumbria. It is not a recent response to "acid rain". Harmful effects of pH are undoubtedly more pronounced in waters that are poor in other dissolved ions. Low concentrations of sodium, potassium, calcium and chloride are especially important and may limit the distributions of some aquatic animals even where pH is above 5.7. The concentration of sulphate ions is usually relatively high but this is not important to the fauna; concentrations are at least two times higher in productive alkaline water-bodies than they are in unproductive acid waters.

Discharge and turbidity of the regulated River Tees. Variance spectrum analysis

High suspended sediment loads may be deleterious to adult salmonids and invertebrates in gravel-bedded streams. Further, the accumulation of fine material in the interstices of the gravel may have an adverse impact on the recruitment of the young stages of salmonids. It is important therefore not only to quantify the rates and degrees of silting but also to identify sediment sources and to determine both, the frequency of sediment inputs to the system and the duration of high sediment concentrations. This report explores the application of variance spectrum analysis to the isolation of sediment periodicities. For the particular river chosen for examination the method demonstrated the essentially undisturbed nature of the catchment. The regulated river chosen for examination is the River Tees in Northern England. Variance spectrum analysis was applied to a series of over 4000 paired daily turbidity and discharge readings.

Strategic ecosystem studies of large slow flowing lowland rivers. Progress report: April - October 1989

This report covers the period April to September, 1989. During this period sampling of invertebrates has concentrated on planktonic animals and those associated with one of the dominant macrophytes in the system, Nuphar lutea, the yellow water lily, since these are particularly important in the diets of larval and juvenile cyprinid fish. A proportion of samples has been partly analysed and some preliminary data are presented here.

Molecular biomarkers and toxic consequences of impact by organic pollution in aquatic organisms

Organic contaminants are readily bioaccumulated by aquatic organisms. Exposure to and toxic effects of contaminants can be measured in terms of the biochemical responses of the organisms (i.e. molecular biomarkers). The hepatic biotransformation enzyme cytochrome P4501A (CYP1A) in vertebrates is specifically induced by organic contaminants such as aromatic hydrocarbons, PCBs and dioxins, and is involved in chemical carcinogenesis via catalysis of the covalent binding of organic contaminants to DNA (DNA-adducts). Hepatic CYP1A induction has been used extensively and successfully as a biomarker of organic contaminant exposure in fish. Fewer but equally encouraging studies in fish have used hepatic bulky, hydrophobic DNA-adducts as biomarkers of organic contaminant damage. Much less is known of the situation in marine invertebrates, but a CYPlA-like enzyme with limited inducibility and some potential for biomarker application is indicated. Stimulation of reactive oxygen species (ROS) production is another potential mechanism of organic contaminant-mediated DNA and other damage in aquatic organisms. A combination of antioxidant (enzymes, scavengers) and pro-oxidant (oxidised DNA bases, lipid peroxidation) measurements may have potential as a biomarker of organic contaminant exposure (particularly those chemicals which do not induce CYP1A) and/or oxidative stress, but more studies are required. Both CYP1A- and ROS-mediated toxicity are indicated to result in higher order deleterious effects, including cancer and other aspects of animal fitness.

Biodiversity in drinking water distribution systems:a brief review

In drinking water distribution systems, three groups of living organisms are usually found in the biofilm and circulating water: heterotrophic bacteria, free-living protozoa, and macro-invertebrates. Indirect evidence suggests that protozoa grazing in distribution systems can partially eliminate biomass production and accidental microbiological pollution. This paper examines the biodiversit in drinking water distribution systems.

Home range and habitat use by Kemp's Ridley turtles in West-Central Florida

The Kemp's ridley turtle (Lepidochelys kempii) is an endangered species whose recovery depends in part on the identification and protection of required habitats. We used radio and sonic telemetry on subadult Kemp's ridley turtles to investigate home-range size and habitat use in the coastal waters of west-central Florida from 1994 to 1996. We tracked 9 turtles during May-August up to 70 days after release and fou.ld they occupied 5-30 km2 foraging ranges. Compositional analyses indicated that turtles used rock outcroppings in their foraging ranges at a significantly higher proportion than expected. based on availability within the study area. Additionally. turtles used live bottom (e.g .• sessile invertebrates) and green macroalgae habitats significantly more than seagrass habitat. Similar studies are needed through'mt the Kemp's ridley turtles' range to investigate regional and stage-specific differences in habitat use. which can then be used to conserve important foraging areas.

Biological report - fish mortality, River Conder, 21.7.79

Following a large scale fish mortality caused by a considerable spillage of a pentachlbrophenol-based disinfectant from a mushroom farm, a biological survey of the river Conder was undertaken on 23.7.79. A spillage of this same make of disinfectant from this mushroom farm in February 1976 caused a similar large scale fish mortality. On that occasion, the pollution appeared to have little effect on the benthic invertebrates of the river Conder, with no dead organisms found, although the small beck which received the spillage was quite badly affected. This recent spillage of disinfectant involved a considerably greater volume (approximately 900 gallons) than the 1976 discharge and so this report looks at whether invertebrate fauna of the main river were affected on this occasion. Kick samples were taken at a number of sites in the river Conder from the confluence with the polluted beck to Conder Green. A control sample was also taken upstream of the confluence with the polluted beck. All samples were examined on site and live and dead invertebrates noted and identified as accurately as possible.

Prey preference of lingcod (Ophiodon elongatus), a top marine predator: implications for ecosystem-based fisheries management

Many highly exploited ecosystems are managed on the basis of single-species demographic information. This management approach can exacerbate tensions among stakeholders with competing interests who in turn rely on data with notoriously high variance. In this case study, an application of diet and dive survey data was used to describe the prey preference of lingcod (Ophiodon elongatus) in a predictive framework on nearshore reefs off Oregon. The lingcod is a large, fast-growing generalist predator of invertebrates and fishes. In response to concerns that lingcod may significantly reduce diminished populations of rockfishes (Sebastes spp.), the diets of 375 lingcod on nearshore reefs along the Oregon Coast were compared with estimates of relative prey availability from dive surveys. In contrast to the transient pelagic fishes that comprised 46% of lingcod diet by number, rockfishes comprised at most 4.7% of prey items. Rockfishes were the most abundant potential prey observed in dive surveys, yet they were the least preferred. Ecosystem-based fisheries management (EBFM) requires information about primary trophic relationships, as well as relative abundance and distribution data for multiple species. This study shows that, at a minimum, predation relative to prey availability must be considered before predator effects can be understood in a management context.

Comparison of echogram measurements against data expectations and assumptions for distinguishing seafloor substrates

Defining types of seafloor substrate and relating them to the distribution of fish and invertebrates is an important but difficult goal. An examination of the processing steps of a commercial acoustics analyzing software program, as well as the data values produced by the proprietary first echo measurements, revealed potential benef its and drawbacks for distinguishing acoustically distinct seafloor substrates. The positive aspects were convenient processing steps such as gain adjustment, accurate bottom picking, ease of bad data exclusion, and the ability to average across successive pings in order to increase the signal-to-noise ratio. A noteworthy drawback with the processing was the potential for accidental inclusion of a second echo as if it were part of the first echo. Detailed examination of the echogram measurements quantified the amount of collinearity, revealed the lack of standardization (subtraction of mean, division by standard deviation) before principal components analysis (PCA), and showed correlations of individual echogram measurements with depth and seafloor slope. Despite the facility of the software, these previously unknown processing pitfalls and echogram measurement characteristics may have created data artifacts that generated user-derived substrate classifications, rather than actual seafloor substrate types.

Age- and length-at-maturity of female arrowtooth flounder (Atheresthes stomias) in the Gulf of Alaska

Arrowtooth flounder (Atheresthes stomias) has had the highest abundance of any groundfish species in the Gulf of Alaska since the 1970s (Matarese et al., 2003; Turnock et al., 2005; Blood et al., 2007); however, commercial catches have been restricted because Pacific halibut (Hippoglossus stenolepis) are caught as bycatch in the fishery. Arrowtooth flounder plays a key role in the ecosystem because it is a dominant organism within the food web, both as an apex predator of fish and invertebrates, as well as an important prey for walleye pollock (Theragra chalcogramma; Aydin et al., 2002). Walleye pollock is the dominant groundfish in the Bering Sea, a principal groundfish in the Gulf of Alaska, and the primary prey for marine mammals. The distribution of arrowtooth flounder extends from Cape Navarin and the eastern Sea of Okhotsk in Russia, across the Bering Sea, Aleutian Islands, Gulf of Alaska, and south to the coast of central California (Shuntov, 1964; Britt and Martin, 2001; Chetvergov, 2001; Weinberg et al., 2002; Zenger, 2004). Because of the importance of arrowtooth flounder in the marine ecosystem of A laska, a maturity study of this species was undertaken to determine age-at-maturity, which is essential for age-based stock management models. Before these results, management has had to rely upon a length-at-maturity-based estimate (Zimmermann, 1997) to manage stocks in the Gulf of Alaska (GOA), Bering Sea, and Aleutian Islands. The central GOA was selected as the location for this maturity study Age- and length-at-maturity of female arrowtooth flounder (Atheresthes stomias) in the Gulf of Alaska because it contains approximately 70% of the total Gulf of Alaska arrowtooth flounder biomass (1.9×106 t, age 3 and older)— the highest percentage in the world (Shuntov, 1964; Britt and Martin, 2001; Weinberg et al., 2002; Wilderbuer and Nichol, 2006).

Review of the crevalle jacks, Caranx hippos complex (Teleostei: Carangidae), with a description of a new species from West Africa

The Caranx hippos species complex comprises three extant species: crevalle jack (Caranx hippos) (Linnaeus, 1766) from both the western and eastern Atlantic oceans; Pacific crevalle jack (Caranx caninus) Günther, 1868 from the eastern Pacific Ocean; and longfin crevalle jack (Caranx fischeri) new species, from the eastern Atlantic, including the Mediterranean Sea and Ascension Island. Adults of all three species are superficially similar with a black blotch on the lower half of the pectoral fin, a black spot on the upper margin of opercle, one or two pairs of enlarged symphyseal canines on the lower jaw, and a similar pattern of breast squamation. Each species has a different pattern of hyperostotic bone development and anal-fin color. The two sympatric eastern Atlantic species also differ from each other in number of dorsal-and anal-fin rays, and in large adults of C. fischeri the lobes of these fins are longer and the body is deeper. Caranx hippos from opposite sides of the Atlantic are virtually indistinguishable externally but differ consistently in the expression of hyperostosis of the first dorsalfin pterygiophore. The fossil species Caranx carangopsis Steindachner 1859 appears to have been based on composite material of Trachurus sp. and a fourth species of the Caranx hippos complex. Patterns of hyperostotic bone development are compared in the nine (of 15 total) species of Caranx sensu stricto that exhibit hyperostosis.