Environmental impact studies on marine communities: Pragmatical considerations

Abstract The measurement of changes in the structure of natural marine communities is widely used for the detection and monitoring of man's impact on the sea. Such studies are almost always a compromise between the scientific ideal and political, financial and logistical constraints. This paper considers a number of these constraints, suggests some possible solutions, and discusses the consequences (in terms of loss of information) of adopting strategies which might be considered suboptimal. Identification of all organisms in a community to species level is a major time and cost constraint. Many recent studies have shown that very little information is lost by working at a taxonomic level higher than species (e.g. family or even phylum). This implies a functional coherence of species within each higher taxon. Indeed, there are theoretical reasons, and some empirical evidence, for supposing that community responses to human perturbations may be more easily detected above the noise of natural variability by working at high taxonomic levels. Many environmental impacts, for example oil spillages from tankers, are accidental and it is unusual to have the luxury of a time-series of data from the site prior to the incident. Good spatial control samples may also be difficult to obtain in a heterogeneous environment. Absolute rather than comparative measures of community degradation are valuable in this context. Methods which fall into this category include comparisons of community structure with some theoretical expectation or with empirical‘training’ data, comparing attributes of community structure that respond differently to perturbation, or identifying highly conservative properties of unperturbed communities that are modified in a predictable way by perturbation. All studies are selective with regard to which components and attributes of the biota should be investigated. The choice frequently depends on local expertise and research interests, rather than on an objective decision about what biological data are most appropriate for the problem in hand. The paper concludes by a discussion of the relative merits of the various alternatives.     

Snorkelers impact on fish communities and algae in a temperate marine protected area

Multiple-use marine protected areas (MPAs) are used to manage marine resources, allocate space to different users and reduce conflicts while protecting marine biodiversity. In the Mediterranean, MPA managers are increasingly interested in containing the effects of coastal recreation within underwater trails, but snorkelers impacts on the surrounding ecosystem remain largely unknown. In a Mediterranean MPA, an underwater snorkeling trail was established to concentrate snorkelers and increase their awareness of marine habitats and species. The high level of summer frequentation may have negative impacts on the surrounding environment through trampling on the sessile flora or disturbance to the vagile fauna. We used a before-after-control-impact (BACI) design to analyse these potential human impacts. The structure of macroalgae and fish assemblages were used as indicators. Permutational multivariate analyses of variance (PERMANOVA) were carried out to assess potential temporal and spatial changes of the indicators between the trail and a control location within the adjacent no-take/no-use area. Fish communities and macroalgae were subjected to natural temporal trends but no significant impacts of snorkelers were found. Four reasons could explain the absence of snorkelers impact on the surrounding marine environment: (1) the absence of very fragile organisms within the trail (and the control no-take/no-use area) such as gorgonians or bryozoans; (2) the life cycle of the algae with a natural decreasing trend in summer, corresponding to the trail opening period; (3) only a few snorkelers are practicing apnoea; and (4) the information at the entrance and along the trail may influence the snorkelers’ behaviour.     

Regional effects as important determinants of local diversity in both marine and terrestrial systems

Community ecologists have struggled to create unified theories across diverse ecosystems, but it has been difficult to acertain whether marine and terrestrial communities differ in the mechanisms responsible for structure and dynamics. One apparent difference between marine and terrestrial ecology is that the influence of regional processes on local populations and communities is better established in the marine literature. We examine three potential explanations: 1) influential early studies emphasized local interactions in terrestrial communities and regional dispersal in marine communities. 2) regional‐scale processes are actually more important in marine than in terrestrial communities. 3) recruitment from a regional species pool is easier to study in marine than terrestrial communities. We conclude that these are interrelated, but that the second and especially the third explanations are more important than the first. We also conclude that in both marine and terrestrial systems, there are ways to improve our understanding of regional influences on local community diversity. In particular, we advocate examining local vs regional diversity relationships at localities within environmentally similar regions that differ in their diversity either because of their sizes or their varying degrees of isolation from a species source.     

On the direct impact of ice on marine benthic communities, a review

Ice has a significant impact on the polar and sub-polar benthos, but relationships between corresponding physical and biological processes are not yet sufficiently understood. Sea ice contributes to a vertical zonation in shallow waters, which also experience other important disturbances. Due to the length of the non-glaciated coastline, sea ice is of greater relevance in the north than in the south. Scouring by icebergs and ridged sea ice causes an increased diversity when different recolonisation stages coexist. Frequently scoured areas do not recover, especially in the Antarctic, due to slow growth rates of the fauna. Iceberg grounding in the Arctic is mainly restricted to the western Eurasian and northeastern American shelf, including Greenland. Around Antarctica, scouring is more evenly distributed. Glacier termini prevent sessile animals from settling in their proximity where only few motile species occur.     

Interspecific variation in life history relates to antipredator decisions by marine mesopredators on temperate reefs

As upper-level predatory fishes become overfished, mesopredators rise to become the new 'top' predators of over-exploited marine communities. To gain insight into ensuing mechanisms that might alter indirect species interactions, we examined how behavioural responses to an upper-level predatory fish might differ between mesopredator species with different life histories. In rocky reefs of the northeast Pacific Ocean, adult lingcod (Ophiodon elongatus) are upper-level predators that use a sit-and-wait hunting mode. Reef mesopredators that are prey to adult lingcod include kelp greenling (Hexagrammos decagrammus), younger lingcod, copper rockfish (Sebastes caurinus) and quillback rockfish (S. maliger). Across these mesopredators species, longevity and age at maturity increases and, consequently, the annual proportion of lifetime reproductive output decreases in the order just listed. Therefore, we hypothesized that the level of risk taken to acquire resources would vary interspecifically in that same order. During field experiments we manipulated predation risk with a model adult lingcod and used fixed video cameras to quantify interactions between mesopredators and tethered prey (Pandalus shrimps). We predicted that the probabilities of inspecting and attacking tethered prey would rank from highest to lowest and the timing of these behaviours would rank from earliest to latest as follows: kelp greenling, lingcod, copper rockfish, and quillback rockfish. We also predicted that responses to the model lingcod, such as avoidance of interactions with tethered prey, would rank from weakest to strongest in the same order. Results were consistent with our predictions suggesting that, despite occupying similar trophic levels, longer-lived mesopredators with late maturity have stronger antipredator responses and therefore experience lower foraging rates in the presence of predators than mesopredators with faster life histories. The corollary is that the fishery removal of top predators, which relaxes predation risk, could potentially lead to stronger increases in foraging rates for mesopredators with slower life histories.     

Egg predation in forest bird communities on islands and mainland

Summary To examine if differences in egg predation rates could explain differences in bird community composition, egg predation was studied in two years on small islands in a South Swedish lake and on the nearby mainland using both natural and artificial nests.In plots with similar vegetation, the combined density of ground- and tree-nesting bird species did not differ between the islands and the mainland. Egg predation rates were similar on islands and the mainland for natural Turdus nests in two years, and for artificial Turdus and Phylloscopus nests. Unmarked and unvisited experimental nests suffered similar rate of egg predation as marked and visited nests. Egg predation rates were higher on natural nests when artificial nests were also put out, increasing the total nest density. Initial egg predation rates in artificial nests were also higher than later when nest density had decreased by 75%.The egg predators involved differed for artificial Phylloscopus nests between the islands and the mainland. Small mammals were apparently responsible for 29% of the predation on the mainland, but none on the islands. Artificial Turdus nests near crow nests suffered from a higher egg predation rate than nests further away from crow nests. Daily survival rates of Turdus nests increased from the laying to the incubation and further to the fledging state.Egg predation can not explain differences in bird community composition between islands and mainland in the present case.     

Mammalian species richness on islands on the Sunda Shelf,Southeast Asia

Summary A rich mammalian fauna is found on islands that lie on the Sunda Shelf, a continental shelf extending from Vietnam to Borneo and Java that was periodically exposed as dry land during the Pleistocene. The correlation between log of island area and number of species is high (r ²=0.94); the slope of the curve is moderate (z=0.235). Distance from small islands to source areas (=Borneo, Sumatra, and the Malay Peninsula) does not appear to affect species richness, nor does depth of water to source area (a measure of isolation time). A species-area curve for forest reserves of varying sizes on the Malay Peninsula has a low slope (z=0.104); comparison of the mainlaind and island curves indicates that decreasing island area is strongly correlated with increased extinction. Extinction has left reduced but ecologically balanced sets of species on all islands, except that carnivores are under-represented on all but the largest islands. Initial body size and rarity appear to play a significant role in determining the probability of extinction of individual species.     

Topographic and altitudinal patterns in plant communities on European arctic islands

 Vegetation on Bear Island, Jan Mayen and Spitsbergen was investigated along altitudinal and topographic gradients in order to describe the main patterns in plant community distributions and compare them with those on the mainland. In a numerical classification the communities were distinctly differentiated; however, physiognomically similar Racomitrium and Sanionia communities dominated in most habitats on Bear Island and Jan Mayen. On Spitsbergen, moss-dominated communities prevailed in depression sites. High-altitude sites were occupied either by moss-dominated communities or by variable assemblages of fragmented moss cover and scattered vascular plants. Dwarf shrub and grass heaths that were common on the mainland did not occur on grazer-free Bear Island and Jan Mayen, and were confined to the lowest altitudes on Spitsbergen. The lack of grazers on Bear Island and Jan Mayen accounts in part for the differences in vegetation between the mainland and the islands. Received: 13 December, 1995/Accepted: 13 March, 1996     

Variation between freshwater and terrestrial fungal communities on decaying bamboo culms

Fungal communities on decaying culms of a bamboo host (Phyllostachys bambusoides) from freshwater and adjacent terrestrial habitats were identified. Collections were made at Xiao Bai Long Mountain, Yiliang, Yunnan, China in the winter and summer. In each collection, 100 similar-sized bamboo culms were collected, comprising 50 submerged samples from a stream and 50 terrestrial samples from adjacent riparian vegetation. A total of 82 fungal taxa were recorded from the samples, including 30 ascomycetes and 52 anamorphic fungi. The frequency of occurrence of these fungi were recorded and the Shannon–Weiner indices (H′) were applied to evaluate fungal diversity. The results showed that variation of the fungal diversity between the summer and winter collections was insignificant (0.2<p<0.5). Fungal diversity on submerged bamboo however, was significantly higher than that on terrestrial bamboo (p<0.001). Further findings were that: (1) some commonly recorded freshwater and terrestrial taxa were found in both habitats, but overall there were only 15 overlapping species between the two habitats; (2) the dominant species in each habitat were considerably different, and (3) only a few fungi were dominant, while most species were rare, being recorded only once or twice. Factors responsible for the distribution patterns and variations in composition of the fungal communities are discussed.     

Antibiotic activity of bonellin and hematoporphyrin on marine and terrestrial bacteria

Bonellin, a chlorin extracted fromBonellia viridis (Echiura), and hemaatoporphyrin exhibit a strong antibiotic and bactericidal activity on marine and terrestrial bacteria. This action is enhanced by light. Oxygen consumption and motility of bacteria are also inhibited, while no chemotactic effects are observed. The drugs induce lysis onBacillus subtilis protoplasts, but they are ineffective onMicrococcus lysodeikticus protoplasts.The results are discussed and compared with those obtained with eukariotic cells. Attention is focused on the ecological role of bonellin in the defense mechanism ofBonellia viridis.     

Peat respiration and decomposition in Antarctic terrestrial moss communities

Oxygen uptake by the peat of two Antarctic bryophyte communities (a moss turf and a moss carpet) is converted to organic matter loss and used to derive the rate of decomposition. The decay rates obtained in this way are evaluated in two mathematical models which simulate the accumulation of dead organic matter (DOM) in the communities from the litter production and decomposition rate. Litter production, the extent of DOM accumulations at present on the sites and mean decomposition rates (i.e. fraction of standing crop lost per year) were 409 g m^-2 year^-1, 33.5 kg m^-2 and 0.017 g g^-1 year^-1 in the moss turf and 392 g m^-2 year^-1, 29.6 kg m-² and 0.010 g g^-1 year^-1 in the moss carpet respectively (all weights expressed as dry weight). Aerobic decomposition rate declined with depth in both communities. From the model's predictions it is suggested that the observed decay rate was too high in the moss turf and too low in the carpet. Possible reasons for this are discussed and suggestions made for future work.     

The impact of global change on terrestrial Vertebrates

Examples of the impact of human activities on Vertebrate populations abound, with famous cases of extinction. This article reviews how and why Vertebrates are affected by the various components of global change. The effect of direct exploitation, while strong, is currently superseded by changes in use of all sorts, while climate change has started having significant effects on some Vertebrate populations. The low maximum growth rate of Vertebrate populations makes them particularly sensitive to global change, while they contribute relatively modestly to major ecosystem services. One may conclude that unless they are considered as sentinels of the biological consequences of global changes, their situation will go on strongly deteriorating, in particular under the influence of interactions of different components of global change such as changes in use and climate change.     

Human influence on the terrestrial biota and biotic communities of New Zealand

Alien plants and animals are of major economic and conservation significance in New Zealand. Plant introductions have averaged 11 species per year since European settlement in /840, and distinctive landscapes are being increasingly altered by weeds. Many introduced animals act as disease vectors or threaten native biota. Recent studies of introduced wasps show adverse effects on honey-eating and insectivorous birds. Introduced possums are now known to prey on eggs and nestlings of native birds in addition to their impact on native forests and transmittal of bovine tuberculosis. Research is increasingly focused on finding effective methods of biocontrol.     

Effects of invasive aquatic carrion on soil chemistry and terrestrial microbial communities

Carrion plays a crucial role in the recycling of nutrients and organic matter in ecosystems. Yet, despite their ecological importance, studies addressing the relevance of carrion originated from invasive alien species (IAS) in the interface between aquatic and terrestrial ecosystems are uncommon, especially those assessing belowground effects. In this study, we carried out a manipulative experiment to assess the impact of massive mortalities of the Asian clam Corbicula fluminea (Müller, 1774) as a carrion subsidy evaluating possible effects on the terrestrial soil chemistry and the structure of a microbial (bacteria and fungi) community. We placed five levels of C. fluminea density (0, 100, 500, 1000 and 2000 ind. m^?2) and samples were collected 7, 30 and 90 days after clams’ addition. The results revealed that C. fluminea carrion have a significant effect belowground, especially on nutrients content (mainly NH₄ ⁺, NO₂ ^?, NO₃ ^? and PO₄ ^3?), fungal biomass and fungal and bacterial diversity. Given the predicted increase and intensification of extreme climatic events and the widespread distribution of several aquatic IAS (including bivalve species such as C. fluminea) the ecological importance of these massive mortalities (and resulting carrion) cannot be ignored because they may affect microbial communities with significant impacts on nutrient cycling, even in adjacent terrestrial habitats.     

Brain-specific lipids from marine, lacustrine, or terrestrial food resources: potential impact on early African Homo sapiens

The polyunsaturated fatty acid (PUFA) composition of the mammalian central nervous system is almost wholly composed of two long-chain polyunsaturated fatty acids (LC-PUFA), docosahexaenoic acid (DHA) and arachidonic acid (AA). PUFA are dietarily essential, thus normal infant/neonatal brain, intellectual growth and development cannot be accomplished if they are deficient during pregnancy and lactation. Uniquely in the human species, the fetal brain consumes 70% of the energy delivered to it by mother. DHA and AA are needed to construct placental and fetal tissues for cell membrane growth, structure and function. Contemporary evidence shows that the maternal circulation is depleted of AA and DHA during fetal growth. Sustaining normal adult human brain function also requires LC-PUFA.Homo sapiens is unlikely to have evolved a large, complex, metabolically expensive brain in an environment which did not provide abundant dietary LC-PUFA. Conversion of 18-carbon PUFA from vegetation to AA and DHA is considered quantitatively insufficient due to a combination of high rates of PUFA oxidation for energy, inefficient and rate limited enzymatic conversion and substrate recycling. The littoral marine and lacustrine food chains provide consistently greater amounts of pre-formed LC-PUFA than the terrestrial food chain. Dietary levels of DHA are 2.5–100 fold higher for equivalent weights of marine fish or shellfish vs. lean or fat terrestrial meats. Mammalian brain tissue and bird egg yolks, especially from marine birds, are the richest terrestrial sources of LC-PUFA. However, land animal adipose fats have been linked to vascular disease and mental ill-health, whereas marine lipids have been demonstrated to be protective. At South African Capesites, large shell middens and fish remains are associated with evidence for some of the earliest modern humans. Cape sites dating from 100 to 18 kya cluster within 200 km of the present coast. Evidence of early H. sapiens is also found around the Rift Valley lakes and up the Nile Corridor into the Middle East; in some cases there is an association with the use of littoral resources. Exploitation of river, estuarine, stranded and spawning fish, shellfish and sea bird nestlings and eggs by Homo could have provided essential dietary LC-PUFA for men, women, and children without requiring organized hunting/fishing, or sophisticated social behavior. It is however, predictable from the present evidence that exploitation of this food resource would have provided the advantage in multi-generational brain development which would have made possible the advent of H. sapiens. Restriction to land based foods as postulated by the savannah and other hypotheses would have led to degeneration of the brain and vascular system as happened without exception in all other land based apes and mammals as they evolved larger bodies.     

Effects of UVB radiation on marine phytoplankton communities

The impact of enhanced and reduced UVB radiation (UVBR) on pelagicecosystems was studied during two mesocosm experiments in May and June/July1994. The ambient UVBR exposure was either reduced with mylar foil orartificially enhanced with UVB fluorescent tubes. Developments in thephytoplankton communities were followed during 11 and 8 day periods usingseveral structural and functional parameters. In the May experiment,enhanced UVBR significantly stimulated carbon dioxide fixation, activity ofalkaline phosphatase and content of fatty acids. In the June-Julyexperiment, the effects induced by changed UVBR were smaller with someindications of decreased algal biomass with enhanced UVBR. Several of themeasured parameters indicated that the two experiments representeddifferent stages in the plankton community development. In the Mayexperiment, the community was in a development stage, moving fromnutrient-replete to nutrient-depleted conditions, while the community inJune/July was depleted of nutrients from the start. The stimulating effectsof UVBR in May are suggested to be the secondary effects of aphotochemically induced breakdown of dissolved organic matter, resulting inan increase in available nutrients.     

Widespread fluorescence in terrestrial and marine samples investigated from India

The discovery of green fluorescent protein (GFP) from jellyfish Aequorea victoria has provoked numerous studies to unveil the myriads of biomedical applications. Consequently, several studies also revealed the prevalence of fluorescence in different marine and terrestrial organisms. However, since GFP's discovery or the Nobel prize award on GFP, the fluorescence has not been explored so far from India. The current study presents the widespread fluorescent organisms resources available in India for biomedical and toxicological applications. Fluorescence emission from different plant and animal components were examined by direct observations using UV torchlight. Investigation revealed that blue light excited fluorescence in several organisms. For the first time, this study observed GFP like fluorescence in many terretrial and marine organisms of India. Observations are indicating that fluorescent proteins have essential ecological functions that are yet to be determined. The examined plant and animal components were not bioluminescent. In comparison, the potential untouched research areas on fluorescence aspects are detailed. A thorough review of fluorescent organisms reported hitherto is also provided to spread the current knowledge on fluorescence.