A. C. Pinder

Organic carbon in the Humber rivers

Abstract Dissolved organic carbon (DOC), particulate organic carbon (POC), particulate organic nitrogen (PON), chlorophyll- a , and alkalinity were determined weekly or more frequently in samples from 11 rivers in the Humber catchment, between September 1993 and February 1995. [DOC] varied overall from 1 to 15 mg l −1 , [POC] from 0.2 to 67 mg l −1 , [LOC] from 0.01 to 7.6 mg l −1 and [DIC] from 1 to 52 mg l −1 . For the rivers with predominantly rural catchments, the complex dependence of [DOC] on season and discharge can be interpreted in terms of soil humification and hydrological processes, whereas the inverse dependence of [DOC] on discharge in the more polluted industrial rivers indicates the dominance of point-source effluents. Concentrations of POC depend significantly upon discharge and on concentrations of suspended particulate matter, suggestive of particle mobilisation when physical thresholds are exceeded. During summer months, the ‘living organic carbon’ of algae accounts for much of the POC in all but the most polluted rivers. Fluxes of organic carbon were estimated by combining daily concentrations (measured or interpolated) with discharge data. The contribution of DOC to the annual flux of organic carbon in the different rivers varies from 51 to 80%, the overall contribution being 63%. For both DOC and POC, the main transport to the estuary takes place during the autumn-winter period. For the study rivers, the total flux of organic carbon during the period September 1993 to September 1994 was 73 × 10 9 g a −1 . However, these rivers represent only about two-thirds of the total catchment area of the Humber estuary, and so the true total flux is probably closer to 100 × 10 9 g a −1 .

Nutrient transport in the Humber rivers

Abstract The results of the weekly and storm sample measurement of the nutrient concentrations in ten Humber rivers over one annual cycle are presented. The nutrients include soluble reactive phosphorus (SRP), total dissolved phosphorus (TDP), total phosphorus (TP), nitrate and silicon (soluble reactive silicon). These data are combined with the river discharge data to calculate the nutrient loads discharged into the intertidal zones. The loads are expressed as the nutrient exports normalised with respect to the catchment areas. The results clearly demonstrate that the majority of the nutrient load is transported in autumn/winter storms. The rivers in the south of the region, i.e. Trent, Don, Aire and Calder, have high nutrient exports compared with the rivers in the north of the region such as the Wharfe, Swale, Nidd and Ure. These differences are attributable to the relative importance of effluent discharges and differences in the land use and extent of urbanisation in the regions. With the exception of the R. Derwent, those rivers with a high nitrate export also have the highest SRP export. The results for the R. Swale, the only river having two monitoring sites, highlight the importance of urban and agricultural impacts in the lowland region of the catchment. The export of silicon is least variable, although a sharp spring minimum in concentration, caused by phytoplankton uptake, is evident for the larger rivers such as the R. Trent. The fractionated forms of phosphorus also varied between the rivers but each of the fractions: SRP, (TDP-SRP), (i.e. mainly organophosphorus and inorganic polyphosphates hydrolysed in digestion procedure), and particulate phosphorus, significantly contributed to the load in all the rivers. For example the phosphorus load in the R. Trent is dominated by the SRP fraction, whereas the R. Swale export is highly influenced by the transport of suspended solids, most of which originates from the lowland region between Catterick and the confluence with the R. Ure. The results of intensive hourly sampling through a storm event on the R. Swale demonstrate the importance of the tributaries in the downstream 54 km section on the river. Although the majority (85%) of the water at the downstream site originates from the upland region north of Catterick, the majority of the nitrate (74%) and SRP (78%) originates from the rivers Wiske and Cod Beck as well as minor tributaries in the southern region of the catchment. A detailed mass balance of the section indicates net losses of nitrate, silicon, SRP and TDP from the water column.

Concentrations of suspended chlorophyll a in the Humber rivers

Abstract Concentrations of chlorophyll a have been determined at weekly intervals for all of the major rivers feeding the Humber Estuary since September 1993, as part of the LOIS monitoring programme. Highest concentrations generally occurred in the two southern rivers, the R. Trent and the R. Don, and also in the larger of the northern rivers, the R. Ouse and its main feeder, the R. Ure. High concentrations also developed on occasions in some of the other northern rivers, especially during the summer of 1995 when the unusually dry conditions led to low flows and extended retention times. Heavy pollution levels in the R. Aire and the R. Calder, a major tributary of the Aire, were probably responsible for the consistently low concentrations recorded in these rivers.

TEMPORAL AND SPATIAL VARIATIONS IN THE DIET OF 0 GROUP ROACH (RUTILUS RUTILUS) LARVAE AND JUVENILES IN THE RIVER GREAT OUSE IN RELATION TO PREY AVAILABILITY

0 group roach, (Rutilus rutilus) in the River Great Ouse showed marked ontogenetic changes in their diet. Initial prey were diatoms and Rotifera, followed by Cladocera and other small aquatic invertebrates. From late June onwards, roach in the main river channels switched to feeding on detrital aufwuchs and associated meiofauna on the surface of submerged aquatic plants. This switch did not occur in a marina habitat, where planktonic Cladocera dominated the diet. Between-year differences were observed in the numbers of prey eaten per fish, which largely reflected variations in the abundance of the prey organisms in the water column, or associated with submerged macrophytes.

Techniques for evaluating the spatial behaviour of river fish

Radio-tagging is widely used for studies of movements, resource use and demography of land vertebrates, with potential to combine such data for predictive modelling of populations from individuals. Such modelling requires standard measures of individual space use, for combination with data on resources, survival, dispersal and breeding. This paper describes how protocols for efficient collection of space-use data can be developed during a pilot study, and reviews the ways in which such data can be used for space-use indices that help answer biological questions, with examples from a study of riverine pike (Esox lucius). Analyses of diurnal activity and spatio-temporal correlation were used to assess when to record locations, and analyses of home range increments were used to define the number of location records necessary to assess seasonal ranges. We stress the importance of developing protocols that use minimal numbers of locations from each individual, so that analyses can be based on samples of many individuals. The efficacy of link-distance (e.g. cluster analysis) and location density (e.g. contouring) techniques for spatial analysis for river fish were compared, and the utility of clipping off areas to river banks was assessed. In addition, a new automated analysis was used to estimate distances along river mid-lines. These techniques made it possible to quantify interactions between individuals and their habitat: including a significant increase in core range size during floods, significant preference for deep pools, and a lack of exclusive territories.

Fairy shrimps in distress: a molecular taxonomic review of the diverse fairy shrimp genus Branchinella (Anostraca: Thamnocephalidae) in Australia in the light of ongoing environmental change

Australia, and especially South-Western Australia, is a diversity hotspot for large branchiopod crustaceans. A significant proportion of this diversity is found in the anostracans (Crustacea, Anostraca) and particularly in the diverse genus Branchinella with at least 34 species. Members of this genus are found exclusively in temporary aquatic habitats which are increasingly threatened by secondary salinization and other anthropogenic pressures. The development of adequate conservation strategies is therefore considered a priority. To define conservation units, however, thorough knowledge of the taxonomy and phylogenetic position of extant lineages is essential. We reconstructed a large scale phylogeny of the Australian Branchinella by analyzing the 16S mitochondrial gene of 31 presumed species, complemented with analysis of morphological structures holding taxonomic information. Results revealed the presence of at least three new cryptic species. On the other hand, some Branchinella lineages, surviving in environments subjected to contrasting selection regimes, appeared to be conspecific. This suggests substantial physiological plasticity or important adaptive variation present in some species, potentially enabling them to better cope with environmental change, such as secondary salinization. Overall, these results further illustrate the benefits of combining molecular markers and classic morphological taxonomy and phylogeny to assess biodiversity and define conservation units in cryptic groups.

Habitat utilisation by pike Esox lucius L. during winter floods in a southern English chalk river

Seven pike Esox lucius L., implanted with radio-transmitters, were tracked throughout autumn and winter in the River Frome, a southern English chalk river. During the first flood events of the year, pike remained within the main river channel but during subsequent flood events, pike could also be found in flooded fields, in drainage ditches or in a millstream. Eighty percent of the fixes over flooded land occurred within 10 m of the riverbank, although distances of up to 89 m from the bank were recorded. In ditches, pike could be found over 250 m from the main river. For pike in ditches and flooded fields, distance from the main river channel was positively correlated with discharge. There was individual variation amongst pike for the habitat types selected, with some pike utilising flooded field or ditch habitat more often than others. The proportion of time spent out of the main river channel does not appear to be related to the size of the pike. It is hypothesised that pike are leaving the main river channel to exploit feeding opportunities in the flooded fields and drainage ditches, rather than using these areas as refugia from high flow conditions.

Notes on the diversity and distribution of Australian Naididae and Phreodrilidae (Oligochaeta: Annelida)

This paper provides a summary of the diversity and distribution of Australian naidid and phreodrilid oligochaetes. As for other continents, the Australian naidid fauna consists mostly of cosmopolitan species, although there are indications of greater endemicity than currently recognised. While some naidids are widespread in Australia, others have a northern or a southern bias to their distribution, but few have been recorded in Tasmania. Many new records and species of Phreodrilidae have been documented since the review by Pinder & Brinkhurst (1997a) and these have allowed notions of phreodrilid zoogeography to be refined. The family is still considered particularly diverse in some temperate areas (Tasmania and the far south-west of Western Australia), but surprisingly few species are known from the temperate south-east mainland. Increasingly, new phreodrilid species are being collected from seasonal habitats on granite outcrops in the south-west and from refugial habitats (caves, groundwater and permanent river pools) in drier regions. A complete picture of oligochaete distributions will require much more work and patterns suggested by current data are presented here as hypotheses.

Modelling phytoplankton dynamics in the River Swale, an upland river in NE England

Abstract A mathematical model has been developed to examine the behaviour of the algal community in a fast-flowing river. The model has been applied to data for the River Swale, NE England, over a 1-year period (September 1993–August 1994). The data include environmental variables, chlorophyll a concentration and relative proportions (based on cell counts) of the major algal groups. A resuspension mechanism is proposed for benthic algae entering the overlying water column, which is related to suspended sediment concentration. During the winter period patterns in simulated chlorophyll a then match those in measured chlorophyll a although at a lower level. Results show that peaks in measured chlorophyll a during the summer are related to blooms in the phytoplankton and the benthic algae on the substrate. Further simulations indicate that the benthic community sustains phytoplankton populations during the winter period and enables their subsequent growth during the summer.

DNA-barcoding of invasive European earthworms (Clitellata: Lumbricidae) in south-western Australia

Using DNA-barcoding, we studied the diversity of invasive European earthworms in the south-western corner of Australia. We found six Molecular Operational Taxonomic Units belonging to five morphospecies: Aporrectodea caliginosa, A. trapezoides, Dendrobaena cf. attemsi, Eiseniella tetraedra and Octolasion cyaneum. These were variously collected from indigenous forests and/or alienated land. Two cryptic lineages were found within A. trapezoides, and high intraspecific genetic variation was also found within E. tetraedra—variation that had previously been documented in Europe. Our study demonstrates the usefulness of DNA-barcoding for the identification of earthworms, including cryptic species. Correct identification and high taxonomic resolution is crucial for the monitoring of cryptic diversity, detecting new introductions and monitoring spread of established exotic earthworms.