John O’Halloran

Identifying practical indicators of biodiversity for stand-level management of plantation forests

Identification of valid indicators of biodiversity is a critical need for sustainable forest management. We developed compositional, structural and functional indicators of biodiversity for five taxonomic groups—bryophytes, vascular plants, spiders, hoverflies and birds—using data from 44 Sitka spruce (Picea sitchensis) and ash (Fraxinus excelsior) plantation forests in Ireland. The best structural biodiversity indicator was stand stage, defined using a multivariate classification of forest structure variables. However, biodiversity trends over the forest cycle and between tree species differ among the taxonomic groups studied. Canopy cover was the main structural indicator and affected other structural variables such as cover of lower vegetation layers. Other structural indicators included deadwood and distances to forest edge and to broadleaved woodland. Functional indicators included stand age, site environmental characteristics and management practices. Compositional indicators were limited to more easily identifiable plant and bird species. Our results suggest that the biodiversity of any one of the species groups we surveyed cannot act as a surrogate for all of the other species groups. However, certain subgroups, such as forest bryophytes and saproxylic hoverflies, may be able to act as surrogates for each other. The indicators we have identified should be used together to identify stands of potentially high biodiversity or to evaluate the biodiversity effects of silvicultural management practices. They are readily assessed by non-specialists, ecologically meaningful and applicable over a broad area with similar climate conditions and silvicultural systems. The approach we have used to develop biodiversity indicators, including stand structural types, is widely relevant and can enhance sustainable forest management of plantations.

Aspects of Assaying Sediment Toxicity in Irish Estuarine Ecosystems

The toxicity of surface sediments collected from eight estuarine sites around the Irish coast was assessed in March 1997 using a whole sediment bioassay. Two molluscan species, Tapes semidecussatus (1 + age class) and Scrobicularia plana (unknown age) were exposed to test sediments for 21 days. Survival, morphometric, behavioural and histochemical measurements were taken during the 21 day bioassay. 100% mortality occurred in both species in sediments from one site in Dublin Bay within 18 days of initial exposure. 100% survival of T. semidecussatus was observed in all but four of the test sediments to which it was exposed during this study. The animal condition and wet tissue weight of T. semidecussatus decreased for all sediments during the bioassay. 95% survival of S. plana was observed after 21 days exposure to Youghal (reference) sediment. Condition and wet tissue weight of S. plana increased in all test sediments during the bioassay, however, there was significant variation in wet tissue weight of this species on day 25 of the bioassay in all test sediments. There was significant variation in the burrowing behaviour of S. plana during the bioassay. Lipofuscin accumulation was observed in the digestive diverticula of T. semidecussatus exposed to all test sediments with the exception of Youghal (reference). The potential for both species as bioassay organisms is discussed.

Alumina nanoparticles enhance growth of Lemna minor

The industrial use of nanoparticles is rapidly increasing, and this has given rise to concerns about potential biological impacts of engineered particles released into the environment. So far, relatively little is known about uptake, accumulation and responses to engineered nanoparticles by plants. In this study, the effects of alumina nanoparticles on growth, morphology and photosynthesis of Lemna minor were quantified. It was found that alumina nanoparticles substantially increase biomass accumulation of L. minor. Such a stimulatory effect of alumina nanoparticles on growth has not been reported previously. Enhanced biomass accumulation was paralleled by morphological adjustments such as increased root length and number of fronds per colony, and by increased photosynthetic efficiency. Metal nanoparticles have previously been shown to enhance the energy transfer efficiency of isolated reaction centres; therefore it is proposed that the mechanism underlying the alumina mediated enhancement of biomass accumulation in L. minor is associated with increased efficiencies in the light reactions of photosynthesis.

The effects of salinity on the Manila clam (Ruditapes philippinarum) using the neutral red retention assay with adapted physiological saline solutions

This study investigated the internal osmotic regulatory capabilities of the Manila clam (Ruditapes philippinarum) following in vivo exposure to a range of salinities. A second objective was to measure the health status of the Manila clam following exposure to different salinities using the neutral red retention (NRR) assay, and to compare results using a range of physiological saline solutions (PSS). On exposure to seawater of differing salinities, the Manila clam followed a pattern of an osmoconformer, although they seemed to partially regulate their circulatory haemolytic fluids to be hyperosmotic to the surrounding aqueous environment. Significant differences were found when different PSS were used, emphasizing the importance of using a suitable PSS to reduce additional osmotic stress. Using PSS in the NRR assay that do not exert additional damage to lysosomal membrane integrity will help to more accurately quantify the effects of exposure to pollutants on the organism(s) under investigation.

The impact of catchment conifer plantation forestry on the hydrochemistry of peatland lakes

The hydrochemistry of 26 small blanket bog lakes was examined to assess the impact of conifer plantation forestry on lake water chemistry. Lakes were selected from three distinct catchment land use categories: i) unplanted blanket bog only present in the catchment, ii) mature (closed-canopy) conifer plantation forests only present in the catchment and iii) catchments containing mature conifer plantation forests with recently clearfelled areas. All three catchment land uses were replicated across two geologies: sedimentary (sandstone) and igneous (granite). Lakes with afforested catchments across both geologies had elevated concentrations of phosphorus (P), nitrogen (N), total dissolved organic carbon (TDOC), aluminium (Al) and iron (Fe), with the highest concentrations of each parameter recorded from lakes with catchment clearfelling. Dissolved oxygen was also significantly reduced in the afforested lakes, particularly the clearfell lakes. Analysis of runoff from a nearby recently clearfelled site revealed high biological and chemical oxygen demands, consistent with at least part of the elevated concentrations of TDOC emanating from clearfelled sites having higher biochemical lability. Inorganic fertilisers applied at the start of the forest cycle, the decay of the underlying peat soil and accumulated surface tree litter, and leachate from felled trees are the likely sources of the elevated concentrations of plant nutrients, TDOC, heavy metals and major ions, with excessive peat soil disturbance during clearfelling likely exacerbating the runoff into lakes. Our study has demonstrated a clear, deleterious impact of conifer plantations on the water quality draining from blanket bog catchments, with major implications for the management of afforested peatlands.

The value of plantation forests for plant, invertebrate and bird diversity and the potential for cross-taxon surrogacy

As the area of plantation forest expands worldwide and natural, unmanaged forests decline there is much interest in the potential for planted forests to provide habitat for biodiversity. In regions where little semi-natural woodland remains, the biodiversity supported by forest plantations, typically non-native conifers, may be particularly important. Few studies provide detailed comparisons between the species diversity of native woodlands which are being depleted and non-native plantation forests, which are now expanding, based on data collected from multiple taxa in the same study sites. Here we compare the species diversity and community composition of plants, invertebrates and birds in Sitka spruce- (Picea sitchensis-) dominated and Norway spruce- (Picea abies-) dominated plantations, which have expanded significantly in recent decades in the study area in Ireland, with that of oak- and ash-dominated semi-natural woodlands in the same area. The results show that species richness in spruce plantations can be as high as semi-natural woodlands, but that the two forest types support different assemblages of species. In areas where non-native conifer plantations are the principle forest type, their role in the provision of habitat for biodiversity conservation should not be overlooked. Appropriate management should target the introduction of semi-natural woodland characteristics, and on the extension of existing semi-natural woodlands to maintain and enhance forest species diversity. Our data show that although some relatively easily surveyed groups, such as vascular plants and birds, were congruent with many of the other taxa when looking across all study sites, the similarities in response were not strong enough to warrant use of these taxa as surrogates of the others. In order to capture a wide range of biotic variation, assessments of forest biodiversity should either encompass several taxonomic groups, or rely on the use of indicators of diversity that are not species based.

A preliminary study on the effects of oyster culturing structures on birds in a sheltered Irish estuary

This study investigated the species composition, numbers and behaviour of birds in an intertidal oyster culture area in Cork Harbour . These data were compared to a nearby area free of aquaculture within the same estuary in March 1999. Species which occurred in the aquaculture free area were also observed in the trestle-area. The most abundant species were oystercatcher Haematopus ostralegus, redshank Tringa totanus, dunlin Calidris alpina, curlew Numenius arquata, black-headed gull Larus ridibundus and common gull Larus canus. Oystercatcher, curlew, black-headed gull and common gull occurred in significantly lower numbers in the trestle area, while for redshank and dunlin the differences were not significant. The percentage of birds feeding did not differ between the two areas. Oystercatcher, redshank, dunlin and curlew mostly fed in both areas. In contrast, black-headed gull and common gull generally did not feed, but surveyed the area. Whether the trestles were covered by oyster bags or not did not have any effect on the number of birds except for the dunlin. Dunlin were significantly more frequent beneath the trestles with bags compared with those without bags. In general, the percentage of birds feeding did not differ between areas. Interspecies differences occurred with regard to the position occupied by birds at the trestles. Oystercatcher, redshank and curlew spent more time underneath the trestles. Dunlin, black-headed gulls and common gulls did not differ in numbers underneath or on top of the trestles. These preliminary observations at a single time period give some insight as to the potential interactions between shellfish aquaculture and intertidal birds.

Effects of contaminated sediment from Cork Harbour, Ireland on the cytochrome P450 system of turbot.

Hatchery-reared juvenile turbot (Scophthalmus maximus L.) were exposed for 3 weeks, under laboratory conditions, to inter-tidal sediments collected from polluted sites in Cork Harbour (Whitegate and Agahda) and a reference site at Ballymacoda Co., Cork, Ireland. The potential of the sediment exposure to induce cytochrome P450 activities and CYP1A1 in the fish was assessed. Chemical analysis revealed that the sediments originating from the reference and harbour sites were contaminated principally with PAHs-the harbour sites having double the levels of those at the reference site. Following 3 weeks exposure to the sediments western blotting demonstrated a strong immunogenic response for CYP1A1 in the liver, but not for gill or intestine. P450 activities were generally significantly higher than those exposed to reference site sediment. Liver was the most responsive tissue with significantly greater P450 activities compared with gill and intestinal tissues.

The importance of non‐crop vegetation for bird diversity in Sitka spruce plantations in Ireland

Capsule Open spaces and areas dominated by broadleaved trees make an important contribution to the bird diversity of conifer plantations.

Adaptation and validation of a radioimmunoassay kit for measuring plasma cortisol in turbot.

Levels of cortisol in fish blood provide quantitative information on the degree of stress induced by a variety of stressors. It is also useful in describing the social status of individual fish within groups. The commercial production of radioimmunoassay (RIA) kits, such as the DPC Coat-A-Count radioimmunoassay kit, has considerably reduced the effort required for cortisol measurement. These kits employ human plasma based cortisol standards which are not compatible for use with non mammalian species such as fish e.g. turbot, Scophthalmus maximus (Rafinesque), blood due to the interference effect of lipids and steroid binding proteins present in the plasma. In this study the DPC kit was used following the removal of these lipids and steroid binding proteins from the plasma using an ethanol-hexane extraction. Excessive variability in the cortisol values obtained using this method deemed it unsatisfactory in overcoming the problem of incompatibility. A second modification of this technique that was tested involved the preparation of turbot specific standards for use in the preparation of modified standard curves. Using this method, an accuracy of 93.4% was achieved, as opposed to 79.6% using the kit human plasma based standards, and 47.1% using samples following lipid removal using an ethanol-hexane extraction. Based on analysis of accuracy, precision and reproducibility it is concluded that commercially available cortisol kits are suitable for use with turbot plasma, but a number of minor modifications are necessary.