Distinctiveness of macroinvertebrate communities in turloughs (temporary ponds) and their response to environmental variables

Published in: Aquatic Conservation: Marine and Freshwater Ecosystems

1. Turloughs are a prime example of a water body type that interfaces with both the European Habitats Directive (92/43/EEC) and Water Framework Directive (2000/60/EC) (WFD), highlighting the need for an integrated strategy to protect and manage surface waters and groundwaters. To date, research on turloughs, including their invertebrate communities is limited.
2. Eight turloughs were sampled for their macroinvertebrate communities and water chemistry in April 2007. Faunal samples were collected by means of a simple box sampler.
3. Replicate samples within each turlough clustered together, indicating that a single sample can provide a meaningful description of the turlough invertebrate community. Variation of invertebrate communities within turloughs was nested among turloughs.
4. Hydroperiod influenced mean abundance and taxon richness of macroinvertebrates, but no correlation was found between nutrient status and either mean abundance or taxon richness.
5. Turloughs are priority habitats under the EC Habitats Directive, requiring maintenance of favourable conservation status, which needs to be assessed through monitoring, and effected through appropriate management plans. While the distinctiveness of macroinvertebrate communities across turloughs is conducive to simple and cost-effective monitoring, this also challenges the applicability of the concept of type-specific communities across these highly dynamic ecosystems.

Implications of the spatial variability of macroinvertebrate communities for monitoring of ephemeral lakes. An example from turloughs.

In press. in Hydrobiologia

Turloughs, ephemeral water bodies associated with karstified limestone, are an important habitat found in the West of Ireland. They are a priority habitat under the European Habitats Directive (92/43/EEC) and are groundwater-dependent habitats under the European Water Framework Directive (2000/60/EC; WFD). Sampling to meet the objectives of either Directive requires discrimination of inherent natural variation from anthropogenically induced disturbances and accounting for both spatial and seasonal patterns of biotic distribution. This study reports within- (submerged grassland) and between-habitat (submerged and emergent grassland) variability of macroinvertebrate communities in six turloughs. Two different habitat types were sampled from two turloughs in April 2007, and further assessment of spatial pattern in commonly found submerged grassland habitat was determined from four additional turloughs in spring 2008. While cluster analysis and non-metric multidimensional scaling identified differences in macroinvertebrate community structures between habitats in one out of two turloughs, congruence of invertebrate communities was, nevertheless, greater within than among turloughs. Within-habitat variability of macroinvertebrate communities across sampling locations of submerged grassland habitat was sufficiently low so that samples collected at any location of a turlough can provide a reliable metric of the macroinvertebrate community of a turlough as a whole. A standardized submerged grassland sampling approach for routine turlough sampling is recommended as a pressure response method to fulfil the requirements of the WFD. For a comprehensive conservation assessment, however, as demanded under the EC Habitats Directive, we suggest a multi-habitat sampling approach to obtain a thorough assessment of turlough macroinvertebrate biodiversity.

Ecological Feasibility of Scallop (Argopecten purpuratus) Bottom Culture in Tortugas Bay, Northern Peru

M.Sc. Thesis

El Niño 1997/98 led to the extinction of wide parts of the natural scallop populations in Tortugas Bay (Northern Peru), due to dramatically inflow of terrestrial matter, caused by heavy rainfall in the mountains resulting in strongly increasing sedimentation. Since then the resident fishery association continues to struggle for recuperation of the scallop stock. The present study represents part of an ongoing management program in the Bay of Tortugas and is aimed to verify if a sustainable and profitable management of scallop bottom cultures can be ensured under given biological conditions. It is accompanied by a parallel study on the socio-economic aspects of the resident fisheries community. With the purpose to identify suitable cultivation areas for scallops in the management area, individual growth and mortality was investigated by a tagging experiment and using length-frequency data obtained at natural scallop beds. Furthermore influence of scallop density on their growth and mortality, as related to season and different abiotic conditions were examined. The experiments were carried out from October 2001 to February 2002 at five different sites, of which four were situated within the management area of the Bay while the fifth was chosen at a nearby scallop farm. In conclusion of the received data the bay is identified as suitable for scallop bottom culture and the scallop stock of Tortugas Bay seems to be recovering. Growth rates were highest on sandy substrates in the warmer waters of the Bay and appear strongly influenced by spawning activity. No difference in growth could be found between the investigated densities of 30 and 60 individuals/m². Mortality was highest for small size classes and in areas of high predation pressure, while mortality of larger specimens varied from 0-5 % under predator exclosure. Constant monitoring of growth and mortality rates is suggested to obtain predictable yields of the scallop stock and to prevent further collapses of the resident fishery. Furthermore predator clearance is proposed in order to decrease high mortality rates.

The Effects of Season, Habitat, Hydroperiod and Water Chemistry on the Distribution of Turlough Aquatic Invertebrate Communities

PhD Thesis

This study investigated the effects of season, habitat, hydroperiod and water chemistry on the distribution of turlough aquatic invertebrate communities. This included comparative studies of the macroinvertebrate and cladoceran zooplankton communities across twenty-two turloughs, representing a wide hydromorphological and geographical range. It was investigated how differences in hydrological, geomorphological and trophic regimes would affect turlough invertebrate biodiversity and community structure. A comparative study of macroinvertebrate communities of eight turloughs investigated the association of a gradient of total phosphorus with macroinvertebrate community assemblages. Faunal samples were collected with a box sampler using a stratified sampling approach. Replicate samples in each turlough clustered together, indicating that a single sample can provide a meaningful description of the turlough macroinvertebrate community. Hydroperiod influenced mean taxon richness and abundance but no correlation was found between nutrient status and either mean taxon richness or abundance. Separate studies examined the spatial and temporal variability of macroinvertebrate communities in a subset of four turloughs with varying hydrological and nutrient regimes and tested the influence of different disturbance regimes and habitat characteristics on community dynamics. A two-phased hydrocycle was identified, with permanent residents dominating during the start of the hydrocycle and an increase of ephemeral taxa over time. Disturbance had an important effect on macroinvertebrate community structure in turloughs, with high disturbance generally supporting lower faunal diversity. While habitat specific preferences were found for some taxa of conservation concern, variability of macroinvertebrates within turloughs was nevertheless identified to be less than among turloughs. Macroinvertebrate samples collected in any location of the dominant turlough habitat (submerged grassland) were identified as reliable indicators of ecological change of turloughs. A comparative study of macroinvertebrates and cladoceran zooplankton communities was conducted across all twenty-two turloughs, representing a wide hydromorphological and geographical range. Macroinvertebrates were collected in November 2006 and April 2007 using a stratified sampling approach and cladoceran zooplankton in April 2007 using horizontal hauls with a zooplankton net from the shore and a perspex tube. Varying associations of macroinvertebrate as well as zooplankton communities to environmental variables season, nutrient concentrations, number of habitats sampled and hydroperiod of turloughs were found. Some macroinvertebrate orders and zooplankton species showed significant relationships with chemical descriptors of nutrient enrichment. Season, habitat, hydroperiod and nutrient concentrations all had important influences on turlough invertebrate communities. The inherently variable turlough system needs a flexible sampling approach accounting for invertebrate phenology, with timing and frequency of sampling depending on sampling objectives. Whether more than one habitat is sampled should depend on the aim of the study.

Aquatic Invertebrates in Turloughs

Literature Review