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1.
Benedetti-Cecchi L Bertocci I Micheli F Maggi E Fosella T Vaselli S 《Marine environmental research》2003,55(5):95-458
Marine protected areas (MPAs) are increasingly used as a management tool to preserve species and habitats. Testing hypotheses about the effectiveness of MPAs is important for their implementation and to identify informative criteria to support management decisions. This study tested the general proposition that MPAs affected assemblages of algae and invertebrates between 0.0 and 0.5 m above the mean low water level of rocky coasts on two islands in the Tuscan Archipelago (northwest Mediterranean). Protection was concentrated mainly on the west coasts of the islands, raising the possibility that neither the full range of assemblages nor the relevant scales of variation were properly represented within MPAs. This motivated the comparison of assemblages on opposite sides of islands (habitats). The effects of MPAs and habitat were assessed with a multifactorial sampling design; hypotheses were tested about differences in structure of assemblages, in mean abundance of common taxa and in univariate and multivariate measures of spatial variation. The design consisted of three replicate shores for each condition of protected and reference areas on the west side of each island and three unprotected shores on the eastern side. Assemblages were sampled independently four times on each island between June 1999 and January 2001. At each time of sampling two sites were selected randomly at each of two tidal heights to represent midshore and lowshore assemblages on each shore. Estimates of abundance were obtained using non-destructive sampling methods from five replicate 20x20 cm quadrats at each site. Results indicated differences among habitats in structure of assemblages, in mean abundance of common taxa and in univariate and multivariate measures of spatial variation at the scale of shores. Most of these patterns were inconsistent with the predicted effect of management through MPAs. The data suggest that designation of MPAs in the Tuscan Archipelago should proceed through management of multiple shores and types of habitat selected to guarantee protection to a representative sample of assemblages and to the processes responsible for maintenance of spatial patchiness at different scales. This study also shows that considerations of spatial heterogeneity are important to underpin management decisions about the number, size and location of MPAs. 相似文献
2.
Danielle Schreve Andy Howard Andrew Currant Stephen Brooks Simon Buteux Russell Coope Barnaby Crocker Michael Field Malcolm Greenwood James Greig Phillip Toms 《第四纪科学杂志》2013,28(2):118-130
This paper reports the discovery of a rare partial skeleton of a woolly rhinoceros (Coelodonta antiquitatis Blumenbach, 1799) and associated fauna from a low Pleistocene terrace of the River Tame at Whitemoor Haye, Staffordshire, UK. A study of the sedimentary deposits around the rhino skeleton and associated organic‐rich clasts containing pollen, plant and arthropod remains suggests that the animal was rapidly buried on a braided river floodplain surrounded by a predominantly treeless, herb‐rich grassland. Highlights of the study include the oldest British chironomid record published to date and novel analysis of the palaeoflow regime using caddisfly remains. For the first time, comparative calculations of coleopteran and chironomid palaeotemperatures have been made on the same samples, suggesting a mean July temperature of 8–11 °C and a mean December temperature of between ?22 and ?16 °C. Radiocarbon age estimates on skeletal material, supported by optically stimulated luminescence ages from surrounding sediments, indicate that the rhino lived around 41–43 k cal a BP. The combined geochronological, stratigraphic and palaeoenvironmental evidence places the assemblage firmly within the Middle Devensian (Marine Oxygen Isotope Stage 3). This would agree with other regional evidence for the timing of aggradation for the lowest terrace of the Trent and its tributary systems. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
3.
D. Craw C. G. Rufaut S. Hammit S. G. Clearwater C. M. Smith 《Environmental Geology》2007,51(8):1389-1400
Slopes of an abandoned waste rock at Wangaloa coal mine, south-east New Zealand, have naturally developed variable vegetation
cover over the last 40–60 years. Three distinct areas of revegetation can clearly be identified: dense cover, patchy cover,
and largely unvegetated, and the differences in revegetation success are directly related to the physical properties of different
rock types making up the waste rock substrate. The colonizing plants have become established in largely unweathered rock with
essentially no soil development. Quartz gravel and siltstone waste rock are the two principal rock types forming substrates
for revegetation. The quartz gravel has clasts up to 3 cm, and was derived from the coal-bearing sequence. Siltstone was largely
derived from a Quaternary loess cap on the coal mine area. These two substrates have similar mineral contents, and this mineral
material provides the low level of available nutrients. However, there is little difference in nutrient status or trace element
load of the different substrates, and differences in cohesion, moisture content, and proportion of quartz pebbles control
revegetation success. Finer grained matrix has been flushed from quartz gravel waste rock by rain water, leaving a dry surface
armour layer of quartz pebbles. This surface layer inhibits plant establishment, so quartz gravel waste rock remains largely
unvegetated. Erosion creates deep rills, and steep surfaces creep downslope. In contrast, full vegetation cover was established
on the siltstone waste rock that was cohesive and did not erode. Patchy revegetation was localized by siltstone in mixed quartz
gravel and siltstone substrate. Invertebrate diversity and distribution were closely linked to the spatial patterns of revegetation.
The rate of revegetation and ecosystem recovery was primarily dependent on the proportion of siltstone waste rock in the last
dumped truck load. A quartz pebble content <15% is optimal for plant establishment. 相似文献
4.
Rachel M. Jeffreys Marc S.S. LavaleyeMagda J.N. Bergman Gerard C.A. DuineveldRob Witbaard 《Deep Sea Research Part I: Oceanographic Research Papers》2011,58(4):415-428
Deep-sea benthic communities derive their energetic requirements from overlying surface water production, which is deposited at the seafloor as phytodetritus. Benthic invertebrates are the primary consumers of this food source, with deep-sea fish at the top of the trophic hierarchy. Recently, we demonstrated with the use of baited cameras that macrourid fish rapidly respond to and feed vigorously on large plant food falls mimicked by spinach (Jeffreys et al., 2010). Since higher plant remains are scarce in the deep-sea, with the exception of canyons, where terrestrial material has been observed, these results led us to ask if a more commonly documented plant material i.e. phytodetritus might form a food source for deep-sea fish and mobile scavenging megafauna. We simulated a phytodetritus dump at the seafloor in two contrasting environments (1) the NE Atlantic where carpets of phytodetritus have been previously observed and (2) the oligotrophic western Mediterranean, where the deposition of phytodetritus at the seafloor is a rare occurrence. We recorded the response of the scavenging fauna using an in situ benthic lander equipped with baited time-lapse cameras. In the NE Atlantic at 3000 m, abyssal macrourids and cusk-eels were observed ingesting the phytodetritus. The phytodetrital patch was significantly diminished within 2 h. Abundance estimates calculated from first arrival times of macrourids at the phytodetrital patch in the Atlantic corresponded with abundance estimates from video-transect indicating that fish were attracted to the scent of phytodetrital bait. In contrast to this, in the western Mediterranean at 2800 m a single macrourid was observed investigating the phytodetrital patch but did not feed from it. The phytodetrital patch was significantly diminished within 6.5 h as a result of mainly invertebrate activity. At 1900 m, Lepidion lepidion was observed near the lander and the bait, but did not feed. The phytodetrital patch remained intact until the end of the experiment. In the deployments in the Mediterranean abundance estimates from first arrival times at the bait, corrected for their body size, were lower than estimates obtained from video-transects and trawl catches. This suggests that the Mediterranean fish were not readily attracted to this food source. In contrast, invertebrates in the Balearic Sea were observed ingesting the phytodetritus bait despite the rare occurrence of phytodetritus dumps in the Mediterranean. Stable isotope values of the fish at both study sites, set within the context of the benthic food web, did not demonstrate a strong trophic link to phytodetritus. Fatty acid profiles of these fish indicated a strong link between their lipid pool and primary producers i.e. phytoplankton, which may be attributed to trophic transfer. The usefulness of fatty acid biomarkers in ascertaining deep-sea fish diets is discussed. Our study suggests that the abyssal grenadier C. armatus on the Atlantic Iberian margin is attracted to phytodetritus. However the exact contribution of this food source to the diet of macrourids in this area remains unresolved. 相似文献
5.
E. Fanelli V. PapiolJ.E. Cartes P. RumoloC. Brunet M. Sprovieri 《Deep Sea Research Part I: Oceanographic Research Papers》2011,58(1):98-109
The food-web structure of the epibenthic and infaunal invertebrates on the continental slope of the Catalan Sea (Balearic basin, NW Mediterranean) was investigated using carbon and nitrogen stable isotopes on a total of 34 species, and HPLC pigment analyses for three key species. Samples were collected close to Barcelona (NE Iberian Peninsula), between 650 and 800 m depth and between February 2007 and February 2008. Mean ??13C values ranged from −21.0‰ (small Calocaris macandreae and Amphipholis squamata) to −14.5‰ (Sipunculus norvegicus). Values of ??15N ranged from 4.0‰ (A. squamata) to 12.1‰ (Molpadia musculus). The stable isotope ratios of benthic fauna displayed a continuum of values (e.g. ??15N range of 8‰), confirming a wide spectrum of feeding strategies (from active suspension feeders to predators) and complex food webs. According to the available information on diets of benthic fauna, the lowest values were found for surface deposit feeders (small C. macandrae and the two ophiuroids A. squamata and Amphiura chiajei) and active suspension feeders (Abra longicallus and Scalpellum scalpellum) feeding on different sizes of particulate organic matter (POM), among which small particles may exhibit lower ??15N. High annual mean ??15N values were found among sub-surface deposit feeders, exploiting refractory or frequently recycled organic matter that is enriched in ??15N. Carnivorous polychaetes (Nephtys spp., Oenonidae and Polynoidae) and large decapods (Geryon longipes and Paromola cuvieri) also displayed high ??15N values. ??13C ranges were particularly wide among surface deposit feeders (ranging from −21.0‰ to −16.4‰), suggesting exploitation of POM of both terrigenous and oceanic origins. Correlation between ??13C and ??15N was generally weak, indicating multiple carbon sources, likely due to the consumption of different kinds of sinking particles (e.g. marine snow, phytodetritus, etc.), sedimented and frequently recycled POM, together with macrophyte remains. The stronger ??13C-??15N correlations found in February and April suggest that during the period of water column homogeneization (winter-spring), the benthic community was sustained by phytodetritus inputs originating from the peak of surface primary production in February. Conversely, weaker ??13C-??15N correlations were observed during the period of water column stratification (beginning in June-July), suggesting that the benthic community in this period was sustained, with a delay of ca. 2/3 months, by multiple carbon sources including continental inputs from river discharge (with the maxima in April-May). Thus both advective and vertical fluxes seem to be food sources for benthos on the Catalonian slope. Pigments in the guts of key species were generally degraded, and only the active suspension feeder A. longicallus ingested fresh chlorophyll during periods of high primary production at the surface (February and April 2007). 相似文献
6.
Selenium concentrations have been measured in sediment, fucoid macroalgae and macroinvertebrates from four estuaries of SW England (Yealm, Plym, Looe, Fal). Sediment concentrations ranged from about 0.4 μg g−1 in the Yealm to 1.49 μg g−1 at one site in the Plym. Concentrations in Fucus vesiculosus (0.05–0.31 μg g−1) and F. ceranoides (0.05–0.51 μg g−1) were significantly lower than corresponding concentrations in sediment but there was no correlation between algal and sediment concentrations. Selenium concentrations in Littorina littorea (∼4 μg g−1), Hediste diversicolor (2.82–12.68 μg g−1), Arenicola marina (∼17 μg g−1) and Scrobicularia plana (1.18–6.85 μg g−1) were considerably higher than concentrations in macroalga or sediment, suggesting that Se is effectively accumulated from the diet. Although Se concentrations in some invertebrates exceed toxicity thresholds for the diet of predacious birds and fish, no specific evidence for Se toxicity exists in these estuaries. 相似文献
7.
8.
《Limnologica》2014
Bivalves are remarkable ecosystem engineers and their long-lasting shells may provide important physical structures for benthic organisms. In the last decades the Danube River has experienced great changes in the bivalve fauna, i.e. several native species have been declining and several invasive species have been introduced. The invasive Corbicula fluminea and Sinanodonta woodiana are now widespread and produce large amounts of shells. In this study, we investigated empty shells of native (Anodonta anatina, Unio tumidus) and invasive (C. fluminea, S. woodiana) bivalves (including their mixtures) as benthic substrates and compared them to clay granules (control), which mimics the natural hard substrates in the Danube River (Hungary). Macroinvertebrate colonization was compared between (i) empty shells and control substrate; (ii) different bivalve species (native and invasive) and (iii) three scenarios (before invasion, and short and long time after invasion) by using a mix of empty shells (native, native plus invasive, and invasive species). In comparison to control treatments the empty shells facilitated the presence of amphipods, caddis larvae and isopods, which contributed to a shift in the trophic structure by decreasing the proportion of gathering collectors while increasing the presence of shredders and predators. Several shell traits such as size, outer-shell surface roughness, hardness, thickness, 3D shape and chemical composition may be important attributes in the habitat modifying effects; however, this study could not disentangle which contribute most for the differences found. Given the capability of invasive C. fluminea and S. woodiana to accumulate large amounts of empty shells on several sites of the Danube, its habitat modifying effects can be particularly important, especially on the macroinvertebrate community structure. Moreover, these effects may increase in near future due to the predicted more frequent and severe extreme climatic conditions, which have been responsible for massive mortalities in both species. 相似文献
9.
S.A. Shanahan S.M. NelsonD.M. Van Dooremolen J.R. Eckberg 《Journal of Arid Environments》2011,75(11):1182-1190
The success of riparian restoration projects in the arid southwestern U.S. is often measured in terms of vegetation characteristics such as growth, cover, and structure. Among low-elevation riverine environments within the Colorado River watershed, restoration is typically conducted to improve degraded habitats for birds of conservation concern by replacing the exotic tamarisk (Tamarix ramosissima) with native cottonwoods (Populus spp.) and willows (Salix spp.). The working assumption for many restoration practitioners is that replacing exotic plants with native plants will improve habitat quality and will, therefore, benefit birds. Based on data collected at exotic and restored (i.e., native) sites along the Las Vegas Wash, Nevada, not all birds benefit from restoration. Broad measures of community benefit, including benefits to birds of conservation concern and riparian obligate/dependent birds, were not detected. There were, however, some species-specific benefits. Some environmental variables that were associated with exotic and native sites were significant in explaining the composition of the bird community. For example, the richness of forbs and grass-like plants (a proxy of soil moisture), invertebrate mass, and percent shade (a proxy for canopy characteristics) were important. Considering our results and depending on restoration goals, tamarisk replacement projects may not inherently provide benefits to birds. 相似文献
10.
Yuri D. Zakharov Yasunari ShigetaOlga P. Smyshlyaeva Alexander M. PopovTatiana A. Velivetskaya Tamara B. Afanasyeva 《Cretaceous Research》2011,32(5):623-645
Palaeotemperatures for the Cretaceous of India and Madagascar have been determined on the basis of oxygen isotopic analysis of well-preserved Albian belemnite rostra and Maastrichtian bivalve shells of from the Trichinopoly district, southern India, and Albian nautiloid and ammonoid cephalopods from the Mahajang Province, Madagascar. The Albian (possibly late Albian) palaeotemperatures for Trichinopoly district are inferred to range from 14.9 °C to 18.5 °C for the epipelagic zone, and from 14.3 °C to 15.9 °C for the mesopelagic zone, based on analyses of 65 samples; isotopic palaeotemperatures interpreted as summer and winter values for near-bottom shelf waters in this area fluctuate from 16.3 to 18.5 °C and from 14.9 to 16.1 °C, respectively. The mentioned palaeotemperatures are very similar to those calculated from isotopic composition of middle Albian belemnites of the middle latitude area of Pas-de-Calais in Northern hemisphere but significantly higher than those calculated from isotopic composition of Albian belemnites from southern Argentina and the Antarctic and middle Albian belemnites of Australia located within the warm-temperate climatic zone. Isotopic analysis of early Albian cephalopods from Madagascar shows somewhat higher palaeotemperatures for summer near-bottom shelf waters in this area (20.2-21.6 °C) in comparison with late Albian palaeotemperatures calculated from southern India fossils, but similar winter values (13.3-16.4 °C); however, the latter values are somewhat higher than those calculated from early Albian ammonoids of the tropical-subtropical climatic zone of the high latitude area of southern Alaska and the Koryak Upland. The new isotopic palaeotemperature data suggest that southern India and Madagascar were located apparently in middle latitudes (within the tropical-subtropical climatic zone) during Albian time. In contrast to the Albian fossils, isotope results of well-preserved early Maastrichtian bivalve shells from the Ariyalur Group, Trichinopoly district, are characterised by lower δ18O values (up to −5.8‰) but normal δ13C values, which might be a result local freshwater input into the marine environment. Our data suggest that the early Maastrichtian palaeotemperature of the southern Indian near-bottom shelf waters was probably about 21.2 °C, and that this middle latitude region continued to be a part of tropical-subtropical climatic zone, but with tendency of increasing of humidity at the end of Cretaceous time. 相似文献