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1.
The high plant richness in riparian zones of tropical forest streams and the relationship with an input of organic matter in these streams are not well understood. In this study, we assessed (i) the annual dynamics of inputs of coarse particulate organic matter (CPOM) in a tropical stream; and (ii) the relationship of species richness on riparian vegetation biomass. The fluxes and stock of CPOM inputs (vertical-VI = 512, horizontal-HI = 1912, and terrestrial-TI = 383 g/m2/year) and the benthic stock (BS = 67 g/m2/month) were separated into reproductive parts, vegetative parts and unidentified material. Leaves that entered the stream were identified and found to constitute 64 morphospecies. A positive relationship between species richness and litterfall was detected. The dynamics of CPOM were strongly influenced by rainfall and seasonal events, such as strong winds at the end of the dry season. Leaves contributed most to CPOM dynamics; leaf input was more intense at the end of the dry season (hydric stress) and the start of the rainy season (mechanical removal). Our study show an increase of litter input of CPOM by plant diversity throughout the year. Each riparian plant species contributes uniquely to the availability of energy resources, thus highlighting the importance of plant conservation for maintaining tropical streams functioning.  相似文献   

2.
The tropical riparian zone has a high diversity of plant species that produce a wide variety of chemical compounds, which may be released into streams. However, in recent decades there has been an extensive replacement of tropical native vegetation by Eucalyptus monocultures. Our objective was to compare fungal colonization of Eucalyptus camaldulensis leaves with fungal colonization of native plant species from riparian zones in Brazilian Cerrado (savannah) streams. The fungal colonization and enzymatic activity significantly influenced leaf litter decomposition. Fungal sporulation rates from leaf litter varied significantly with leaf species, with E. camaldulensis showing the highest sporulation rate (1226 conidia mg−1AFDM day−1) and leaf mass loss (23.2 ± 0.9%). This species has the lowest lignin content and highest N concentration among the studied species. Among the studied native species, we observed the highest sporulation rate for Protium spruceanum (271 conidia mg−1AFDM day−1), Maprounea guianensis (268 conidia mg−1AFDM day−1) and Copaifera langsdorffii (196 conidia mg−1AFDM day−1). Overall, native plant species of the Brazilian Cerrado exhibited recalcitrant characteristics and a higher lignin:N ratio. Therefore, variations in the physical and chemical characteristics of the leaf litter could explain the higher decay rate and reproductive activity observed for E. camaldulensis. However, the detritus of this species were colonized almost exclusively by Anguillospora filiformis (99.6 ± 0.4%) and exhibited a reduction in aquatic hyphomycetes species diversity. Our results suggest that the disturbance in the composition of riparian vegetation and consequently, in the diversity of leaf litter input into streams, could change the patterns and rates of leaf litter utilization by microbial decomposers. These changes may have important consequences in the processing of organic matter and, consequently, in the functioning of freshwater ecosystems.  相似文献   

3.
Anthropogenic inputs of crude and refined petroleum hydrocarbons into the sea require knowledge of the effects of these contaminants on the receiving assemblages of organisms. A microcosm experiment was carried out to study the influence of diesel on a free living nematode community of a Tunisian lagoon. Sediments were contaminated by diesel that ranged in concentration from 0.5 to 20 mg diesel kg−1 dry weight (dw), and effects were examined after 90 days. Gradual changes in community structure were revealed depending on the quantity of diesel administrated. In the medium (1 mg diesel kg−1 and 5 mg diesel kg−1 (dw)) and high (10 mg diesel kg−1, 15 mg diesel kg−1 and 20 mg kg−1 (dw)) treated microcosms, most univariate measures, including diversity and species richness, decreased significantly with increasing level of diesel contamination whereas nematode assemblage from the low treated microcosm (0.5 mg diesel kg−1 (dw)) remained unaffected. Results from multivariate analyses of the species abundance data demonstrated that responses of nematode species to the diesel treatments were varied: Chaetonema sp. was eliminated at all doses tested and seemed to be intolerant species to diesel contamination; Pomponema sp. and Oncholaimus campylocercoïdes were significantly affected at all diesel contamination levels but they were not eliminated, these species were categorized as “diesel-sensitive”; Hypodontolaimus colesi, Daptonema trabeculosum and Daptonema fallax which significantly increased respectively at 0.5, 1 and 5 mg diesel kg−1 (dw) concentrations and appeared to be “opportunistic” species at these doses whereas Marylynnia stekhoveni which increased at all high doses (10, 15 and 20 mg diesel kg−1 (dw)) seemed to be a “diesel-resistant” species.  相似文献   

4.
Changes in the water properties and biological characteristics of the highly acidic Hromnice Lake (Western Bohemia) were investigated. This 110-year-old lake, formed as a consequence of the mining of pyritic shales, is permanently meromictic. Two chemoclines separate an extremely acidic (pH ～ 2.6) mixolimnion from a metal-rich anoxic monimolimnion. The absence of spring mixolimnetic turnover due to ice melting and very slow heat propagation through the chemocline with a 6-month delay were observed. Extreme mixolimnetic oxygen maxima (up to 31 mg l?1) in phosphorus-rich lake (PO43? up to 1.6 mg l?1) well correlated with outbursts of phytoplankton. Phytoplankton consist of several acido-tolerant species of the genera Coccomyxa, Lepocinclis, Chlamydomonas and Chromulina. Surface phytoplankton biomass expressed as chlorophyll-a varies from 2 to 140 μg l?1. Multicellular zooplankton are almost absent with the exception of Cephalodella acidophila, a small rotifer occurring in low numbers. Large red larvae of the midge Chironomus gr. plumosus were found at the bottom close to the shore, with larvulae in the open water. Developmental stages (protonemata) of a moss, resembling filamentous algae, dwell in the otherwise plant-free littoral zone.  相似文献   

5.
An invasive crayfish, Cherax quadricarinatus, and several native shrimp species (Macrobrachium acanthurus, Macrobrachium faustinum, Macrobrachium carcinus, Xiphocaris elongata, and Atyidae sp.) found in the Black River Lower Morass (BRLM), a Ramsar Wetland in Jamaica, support subsistence and artisanal fisheries. Management of this fishery requires information on factors that influence their abundance. Consequently, we assessed the effects of seasonality, extreme and double La Niña episodes (in 2011) and elevated atmospheric temperature (in 2011 and 2012) on weekly Decapoda landing data, collected over a period of two years (2010–2012). The catch of native species showed a cyclical trend every 6 months, coinciding with the dry and wet seasons. The invasive crayfish landing showed a reverse trend during the first year, after which no pattern could be discerned. A dynamic factor analysis (DFA) model with two common trends and four explanatory variables (conductivity, mean weekly number of traps hauled, weekly mean water level, and mean dissolved oxygen) was the optimal model to characterize the variation in wet-weight landings. A generalized additive mixed model with an auto-regressive moving average (ARMA) error structure was used to show that the extreme and double La Niñas were associated with lower monthly atmospheric temperature. Sea surface temperature anomaly in region 3 (a proxy to ENSO) and the trend in temperature were then used to predict the wet weight of native shrimp (U-shaped relationship) and the invasive crayfish (reverse-j shaped relationship), respectively. The native shrimp (mean sustainable yield, MSY = 3469 kg and mean catch per fisher = 2.67 kg) and invasive crayfish (MSY = 11 kg and mean catch per fisher = 0.67 kg) are under fished, although populations of the native shrimp are possibly declining, whereas that of the invasive crayfish may be growing. The declining trend may have adverse implications for the stock of the native shrimp species, which has a higher economic value, if fishing pressure is not reduced/restricted or increased on the invasive crayfish, especially during seasonal and/or ENSO related declines in native shrimp stocks.  相似文献   

6.
《Advances in water resources》2005,28(10):1122-1132
During the last 25 years there has been a great interest in deriving aquifer characteristics from outflow data. This analysis has been mainly based of the drainage of a horizontal aquifer after sudden drawdown, using the Boussinesq approximation. Following the general approach of Brutsaert and Lopez [Brutsaert W, Lopez, JP. Basin-scale geohydrologic drought flow features of riparian aquifers in the southern Great Plains. Water Resour Res 1998;34(2):233–40], it was determined that for this geometry the aquifer behavior could be characterized by dQ/dt ∝ Q3 for small t and by dQ/dt ∝ Q3/2 for large t. It was remarked that dQ/dt ∝ Q for large t is often observed. In practice, it is also difficult to determine if dQ/dt ∝ Q3 for small t because this behavior can only be observed over a very short period.Here, we present a similar analysis of aquifer behavior based on the more fundamental Laplace solution for penetrated aquifers. It has been shown that also when the drain does not fully penetrate the aquifer, the solution still produces good results [Szilagyi, J. Sensitivity analysis of aquifer parameter estimations based on the Laplace equation with linearized boundary conditions. Water Resour Res 2003;39(6)]. The Laplace solution quickly shows that dQ/dt ∝ Q for t → ∞ and dQ/dt ∝ Q∞ for t → 0, after sudden drawdown. This analysis reconfirms previous findings concerning long-time behavior. More importantly, the analysis shows that the exponent B in dQ/dt ∝ QB does not have a fixed limited value for short times for the given geometry. Further analysis, however, shows that under certain conditions the relation dQ/dt ∝ Q3 is retained for 0 ≪ t < 1. Detailed examination of the Laplace solution also shows under which types of recharge dynamics a well-identifiable transition takes place between short- and long-term behavior. As long as such a clear transition exists, the aquifer characterization method proposed earlier by Brutsaert and Lopez [Brutsaert W, Lopez, JP. Basin-scale geohydrologic drought flow features of riparian aquifers in the southern Great Plains. Water Resour Res 1998;34(2):233–40] can be applied. It is shown that for a sharp pulse input, the Laplace solution gives similar results as presented by Brutsaert and Lopez [Brutsaert W, Lopez, JP. Basin-scale geohydrologic drought flow features of riparian aquifers in the southern Great Plains. Water Resour Res 1998;34(2):233–40]. For a smooth pulse, the transition becomes unclear. What is “smooth” and “sharp” depends on input and aquifer characteristics, whereby shallow aquifers give clearer transitions than deep aquifers for the same input. The analysis shows that when rain ceases suddenly after the aquifer has come into equilibrium with a steady rain input, a usable transition in the relation between dQ/dt and Q can be found as well. Researchers can use the present analysis to assess whether specific aquifers and recharge events can be used for the previously suggested characterization method.  相似文献   

7.
《Marine pollution bulletin》2012,65(12):2857-2859
Baseline Hg concentration in bycatch fish from the SE Gulf of California were determined in muscle and liver of 19 species. Levels of Hg in muscle were compared with legal limits of this element in national and international legislation. Considering all fish species, mean concentrations in liver (2.458 ± 1.997 μg g−1) were significantly higher (p < 0.05) than in muscle (0.993 ± 0.670 μg g−1). The sequence of averaged Hg concentrations in most ichthyofauna was liver > muscle. Highest level of Hg in muscle (2.556 μg g−1) and liver (7.515 μg g−1) corresponded to Diapterus peruvianus and Ophioscion strabo, respectively. Considering muscle samples, none of the species had levels of Hg above the limit (1.0 μg g−1 wet weight) in the Mexican legislation; with respect to the Japanese (0.4 μg g−1 wet weight) and British (0.3 μg g−1 wet weight) legislations, 26.3% and 31.6% of the species respectively, were above the corresponding limits.  相似文献   

8.
Respiration rates (mg O2 g?1 AFDW h?1) of Leuctra hippopus, Sericostoma personatum, Helodes minuta, Gammarus pulex and Asellus aquaticus were studied across an oxygen gradient at 2.8 and 6.3 °C, corresponding to an expected 3.5 °C increase in Danish winter stream temperature. Species were selected from the Danish Stream Fauna Index (DSFI), representing an expected hierarchy of tolerance towards water quality degradation. We expected that low-ranking, tolerant species (i.e. indicators of bad water quality) would have the capacity to regulate their oxygen uptake relatively independently of oxygen availability (oxy-regulators) and high-ranking, sensitive species (i.e. indicators of good water quality) would be less able to do so (oxy-conformers). For all species respiration rate was higher (although non-significantly) at 6.3 °C. The species’ oxy-regulatory capacity did not consistently reflect their DSFI ranking. As expected, and in accordance with its DSFI ranking, A. aquaticus had the highest oxy-regulatory capacity with the ability to regulate O2 uptake until an oxygen saturation of only 20%, which did not change with increasing temperature, emphasizing the robustness of A. aquaticus towards changes in the environment. S. personatum, H. minuta and G. pulex revealed no oxy-regulatory capacity. In contrast, the plecopteran L. hippopus did display an unexpected oxy-regulatory capacity. Though an increase in temperature changed L. hippopus’ capacity to oxy-regulate (the critical limit increased from 32.5 to 43.5% oxygen), respiration rates did not change significantly in spite of the temperature increase. This result contradicts the general belief that stoneflies, because of their affinity to well oxygenated habitats, are conformers. Our findings call for further studies on the respiratory conformer–regulator concept and its role as an eco-physiological trait for bio-assessment.  相似文献   

9.
《Marine pollution bulletin》2012,64(5-12):402-411
Iron (Fe) plaque formed on mangrove root increased with wastewater discharge, but the extent was species-specific. For Bruguiera gymnorrhiza, Fe plaque concentration was 0.80 mg g−1 root d.wt at Day 0 and increased to 4.59, 6.84 and 7.52 mg g−1 at Day 75 in the fresh water control (FW), synthetic wastewater with pollutant concentrations five times of municipal sewage (5SW) and double of 5SW (10SW) treatments, respectively; the respective increases in Excoecaria agallocha were from 0.70 to 2.37, 10.73 and 13.21 mg g−1. For Acanthus ilicifolius, similar increase was found in 5SW, but all of the plants were dead in 10SW at Day 75. The concentrations of heavy metals and phosphorus immobilized were positively correlated with the amounts of Fe plaque formed, but the regression coefficients varied among species. The performance of mangrove plants in wastewater treatments was related to the Fe plaque formed and its immobilized wastewater-borne pollutants.  相似文献   

10.
Jan Herrmann 《Limnologica》2012,42(4):299-309
A manmade stormwater wetland in Kalmar, SE Sweden, sized 1 ha and receiving water from residential and road areas, was monitored over the first years after inundation with respect to chemistry and biology. Water flow and chemistry was analysed in years 2–4, mainly on a monthly basis, but, in the final year, every second month. This revealed that total nitrogen, according to the Swedish Environmental Quality Criteria (EQC), typically showed moderate or high concentrations, whereas total phosphorous levels were very high or extremely high. Metal (Cd, Cr, Cu, Pb and Zn) concentrations were low or moderate in terms of EQC. Yearly average reduction of nitrogen was 173 kg ha?1 y?1, tending to increase over time, and for phosphorous 12.1 kg ha?1 y?1, tending to decrease. Vegetation analysis was performed in years 1–4 by noting all species in 27 consecutive zones around the wetland system. This showed that one year after filling with water, the vegetation was already well established with >30 plant species in the entire pond system, and this increased only slightly. After four years, the shoreline vegetation cover had become denser, especially with larger graminoids such as common reed (Phragmites australis) and sea club-rush (Bolboschoenus maritimus), and submersed vegetation almost disappeared. There was a tendency for common species to become more dominant, and for less common species to become rarer. Using sweep net sampling of benthic invertebrates during years 0–2, ca 50 species/higher taxa were observed during the first year, largely because of the appearance of many beetles, especially dytiscids. However, these decreased the following years. Apart from these animals, in the first few months the invertebrate colonisation was dominated by chironomids and corixids, whereas later prominent increases were noticed for the isopod Asellus aquaticus, the snail Physa fontinalis, and the mayfly nymph Cloeon dipterum. The results are discussed in terms of wetland values for biodiversity and nutrient reduction, suggesting that these objectives seem possible to combine in stormwater wetlands.  相似文献   

11.
The horizontal and vertical distribution of jellyfish was assessed in the Chiloé Inland sea, in the northern area of the Chilean Patagonia. A total of 41 species of cnidarians (8 siphonophores, 31 hydromedusae, 2 scyphomedusae) were collected. Eleven jellyfish species were recorded for the first time in the area. Species richness was higher in spring than in winter (37 vs. 25 species, respectively). Species such as Muggiaea atlantica, Solmundella bitentaculata, and Clytia simplex were extremely abundant in spring. The total abundance (408,157 ind 1000 m?3) was 18 times higher in spring than in winter (22,406 ind 1000 m?3).The horizontal distribution of the most abundant species (four in winter, five in spring) showed decreasing abundances in the north–south direction in winter and spring. Peak abundances occurred in the northern microbasins (Reloncaví Fjord, Reloncaví and Ancud gulfs), where the water column stability, phytoplankton and zooplankton abundance were higher, compared with the southern microbasins (Corcovado Gulf, Boca del Guafo). During the spring higher jellyfish abundance season, the vertical distribution of the dominant species (except M. atlantica) showed peak values at mid-depth (30–50 m) and in the deepest sampled layer (50–200 m). This vertical distribution pattern reduced seaward transport in the shallowest layer through estuarine circulation and also limited mortality by predation in the more illuminated shallow layers. Thus, jellyfish were able to remain in the interior waters during the season of maximum biological production.  相似文献   

12.
The peridotites from north of the town of Nain in central Iran consist of clinopyroxene-bearing harzburgite and lherzolite with small lenses of dunite and chromitite pods. The lherzolite contains aluminous spinel with a Cr number (Cr# = Cr/[Cr + Al]) of 0.17. The Cr number of spinels in harzburgite and chromitite is 0.38–0.42 and 0.62, respectively. This shows that the lherzolite and harzburgite resulted from <18% of partial melting of the source materials. The estimated temperature is 1100 ± 200 °C for peridotites, the estimated pressure is <15 ± 2.3 kbar for harzburgites and >16 ± 2.3 kbar for lherzolites and estimated fo2 is 10?1±0.5 for peridotites. Discriminant geochemical diagrams based on mineral chemistry of harzburgites indicate a supra-subduction zone (SSZ) to mid-oceanic ridge (MOR) setting for these rocks. On the basis of their Cr#, the harzburgite and lherzolite spinels are analogous to those from abyssal peridotites and oceanic ophiolites, whereas the chromites in the chromitite (on the basis of Cr# and boninitic nature of parental melts) resemble those from SSZ ophiolitic sequences. Therefore, the Nain ophiolite complex most likely originated in an oceanic crust related to supra-subduction zone, i.e. back arc basin. Field observations and mineral chemistry of the Nain peridotites, indicating the suture between the central Iran micro-continent (CIM) block and the Sanandaj–Sirjan zone, show that these peridotites mark the site of the Nain–Baft seaway, which opened with a slow rate of ocean-floor spreading behind the Mesozoic arc of the Sanandaj–Sirjan zone as a result of change of Neo Tethyan subduction régime during middle Cretaceous.  相似文献   

13.
The spontaneous imbibition of water and other liquids into gas-filled fractures in variably-saturated porous media is important in a variety of engineering and geological contexts. However, surprisingly few studies have investigated this phenomenon. We present a theoretical framework for predicting the 1-dimensional movement of water into air-filled fractures within a porous medium based on early-time capillary dynamics and spreading over the rough surfaces of fracture faces. The theory permits estimation of sorptivity values for the matrix and fracture zone, as well as a dispersion parameter which quantifies the extent of spreading of the wetting front. Quantitative data on spontaneous imbibition of water in unsaturated Berea sandstone cores were acquired to evaluate the proposed model. The cores with different permeability classes ranging from 50 to 500 mD and were fractured using the Brazilian method. Spontaneous imbibition in the fractured cores was measured by dynamic neutron radiography at the Neutron Imaging Prototype Facility (beam line CG-1D, HFIR), Oak Ridge National Laboratory. Water uptake into both the matrix and the fracture zone exhibited square-root-of-time behavior. The matrix sorptivities ranged from 2.9 to 4.6 mm s−0.5, and increased linearly as the permeability class increased. The sorptivities of the fracture zones ranged from 17.9 to 27.1 mm s−0.5, and increased linearly with increasing fracture aperture width. The dispersion coefficients ranged from 23.7 to 66.7 mm2 s−1 and increased linearly with increasing fracture aperture width and damage zone width. Both theory and observations indicate that fractures can significantly increase spontaneous imbibition in unsaturated sedimentary rock by capillary action and surface spreading on rough fracture faces. Fractures also increase the dispersion of the wetting front. Further research is needed to investigate this phenomenon in other natural and engineered porous media.  相似文献   

14.
To improve our knowledge about the geochemical and environmental aftermath of Neoproterozoic global glaciations, we analyzed stable isotopes (δ13C, δ18O, δ34S) and elemental concentrations (Ca, Mg, S, Sr, Fe, and Mn) of the ～ 10-m-thick Zhamoketi cap dolostone atop the Tereeken diamictite in the Quruqtagh area, eastern Chinese Tianshan. Available chemostratigraphic data suggest that the Tereeken diamictite is probably equivalent to the Marinoan glaciation. Our new data indicate that organic and carbonate carbon isotopes of the Zhamoketi cap dolostone show little stratigraphic variations, averaging ? 28.2‰ and ? 4.6‰, respectively. In contrast, sulfur isotopes show significant stratigraphic variations. Carbonate associated sulfate (CAS) abundance decreases rapidly in the basal cap dolostone and δ34SCAS composition varies between + 9‰ and + 15‰ in the lower 2.5 m. In the overlying interval, CAS abundance remains low while δ34SCAS rises ～ 5‰ and varies more widely between + 10‰ and + 21‰. The range of δ34Spy of the cap dolostone overlaps with that of δ34SCAS, but direct comparison shows that δ34Spy is typically greater than δ34SCAS measured from the same samples. Hypotheses to explain the observations must account for both the remarkable sulfur isotope enrichment of pyrites and the inverse fractionation. We propose that CAS and pyrite were derived from two isotopically distinct reservoirs in a chemically stratified basin or a basin with a sulfate minimum zone. In this model, CAS was derived from shallow, oxic surface waters with moderate sulfate concentration and depleted in 34S due to the post-glacial influx of sulfur from continental weathering. In contrast, pyrite was derived from anoxic bottom waters (or a sulfate minimum zone) with low sulfate concentration and 34S enrichment due to long-term syn-glacial sulfate reduction. The rapid shift in CAS abundance and sulfur isotope composition within the cap dolostone is interpreted to reflect the mixing of the two reservoirs after initial deglaciation. Comparison with other post-Marinoan cap carbonates shows significant spatial heterogeneity in δ34SCAS, which together with strong temporal variation in δ34SCAS, points to generally low sulfate concentrations in post-Marinoan oceans.  相似文献   

15.
《Marine pollution bulletin》2014,85(1-2):347-362
Species composition and abundance of dinocysts in relation to environmental factors were studied at 123 stations of surface sediment in Bizerte Lagoon. Forty-eight dinocyst types were identified, mainly dominated by Brigantidinium simplex, Votadinum spinosum, Alexandrium pseudogonyaulax, Alexandrium catenella, and Lingulodinum machaerophorum along with many round brown cysts and spiny round brown cysts. Cysts ranged from 1276 to 20126 cysts g−1 dry weight sediment. Significant differences in cyst distribution pattern were recorded among the zones, with a higher cyst abundance occurring in the lagoon’s inner areas. Redundancy analyses showed two distinct associations of dinocysts according to location and environmental variables. Ballast water discharges are potential introducers of non-indigenous species, especially harmful ones such as A. catenella and Polysphaeridium zoharyi, with currents playing a pivotal role in cyst distribution. Findings concerning harmful cyst species indicate potential seedbeds for initiation of future blooms and outbreaks of potentially toxic species in the lagoon.  相似文献   

16.
The propagation features of nighttime whistlers to low-latitude station, Suva (−18.2°, 178.3°, geomag. lat. −22.1°, geomag. long. 253.5°, L=1.15), Fiji, from preliminary observations made during the period from September 2003–2005, are reported. The observations of ELF–VLF signals commenced in September 2003 using the VLF set-up of World Wide Lightning Location Network at our station. The whistlers were observed during the severe magnetic storm of 20–22 November 2003 and moderate magnetic storm of 17–19 July 2005. A whistler with dispersion D=12.7 s1/2 occurred on 22 November at 00:11 h LT. On 20 July at 01:00 h LT, a short whistler with dispersion D=20.9 s1/2 and two whistler events having two-component whistlers with D=15.8, 16.7 s1/2 and 16.7, 17.3 s1/2 were observed. Non-ducted pro-longitudinal mode of the whistler propagation supported by negative latitudinal electron density gradients in the ionosphere that are enhanced by magnetic storms, seems most likely mode of propagation for the whistlers with dispersion of 12.7–17.3 s1/2 to this low-latitude station.  相似文献   

17.
The spectral attenuation of solar irradiation was measured during summer in two types of coastal waters in southern Chile, a north Patagonian fjord (Seno Reloncaví) and open coast (Valdivia). In order to relate the light availability with the light requirements of upper subtidal seaweeds, the saturating irradiance for photosynthesis (Ek) from P–I curves was measured. In addition the UV risk was assessed. Based on the z1% of PAR, the lower limit of the euphotic zone in the studied systems averaged 21 m (Kd 0.24 m?1) in Seno Reloncaví and 18 m (Kd 0.27 m?1) in the coast of Valdivia. Photosynthesis of the studied seaweeds was saturated at markedly lower irradiances than found in their natural depths at the time of the study. Solar radiation penetrating into these depths at both locations largely supports the light requirements for the photosynthesis of subtidal species: 50–160 μmol m?2 s?1 for seaweeds from Seno Reloncaví (7 m tidal range) and 20–115 μmol m?2 s?1 for Valdivia assemblages (2 m tidal range). Optimal light conditions to saturate photosynthesis (Ek) were present at 10–16 m water depth. The attenuation of solar irradiation did not vary significantly between the fjord and coastal sites of this study. However, the underwater light climates to which seaweeds are exposed in these sites vary significantly because of the stronger influence of tidal range affecting the fjord system as compared with the open coastal site. The patterns of UV-B penetration in these water bodies suggest that seaweeds living in upper littoral zones such as the intertidal and shallow subtidal (<3 m) may be at risk.  相似文献   

18.
《Marine pollution bulletin》2009,58(6-12):575-586
Irgarol 1051 (2-methythiol-4-tert-butylamino-6-cyclopropylamino-s-triazine) is an algaecide commonly used in antifouling paints. It undergoes photodegradation which yields M1 (2-methylthio-4-tert-butylamino-6-amino-s-triazine) as its major and most stable degradant. Elevated levels of both Irgarol and M1 have been detected in coastal waters worldwide; however, ecotoxicity effects of M1 to various marine autotrophs such as cyanobacteria are still largely unknown. This study firstly examined and compared the 96 h toxicities of Irgarol and M1 to the cyanobacterium Chroococcus minor and two marine diatom species, Skeletonema costatum and Thalassiosira pseudonana. Our results suggested that Irgarol was consistently more toxic to all of the three species than M1 (96 h EC50 values: C. minor, 7.71 μg L−1 Irgarol vs. >200 μg L−1 M1; S. costatum, 0.29 μg L−1 Irgarol vs. 11.32 μg L−1 M1; and T. pseudonana, 0.41 μg L−1 Irgarol vs. 16.50 μg L−1 M1). Secondly, we conducted a meta-analysis of currently available data on toxicities of Irgarol and M1 to both freshwater and marine primary producers based on species sensitivity distributions (SSDs). Interestingly, freshwater autotrophs are more sensitive to Irgarol than their marine counterparts. For marine autotrophs, microalgae are generally more sensitive to Irgarol than macroalgae and cyanobacteria. With very limited available data on M1 (i.e. five species), M1 might be less toxic than Irgarol; nonetheless this finding warrants further confirmation with additional data on other autotrophic species.  相似文献   

19.
《Marine pollution bulletin》2012,64(5-12):417-423
Sediment samples were collected from 12 locations of Kaohsiung Harbor, Taiwan and analyzed for polycyclic aromatic hydrocarbons (PAHs). Total PAH concentrations varied from 472 to 16,201 ng g−1 dry weight. The highest PAH concentrations were from the industrial zone docks situated in south Kaohsiung Harbor. Diagnostic ratios showed that the possible source of PAHs in the industrial zone dock could be coal combustion while in the other zones it could be petroleum combustion. The toxic equivalent concentrations (TEQcarc) of PAHs varied from 55 to 1964 ng TEQ g−1 dry weight. Higher total TEQcarc values were found at industrial zone docks (from 1404 to 1964 ng TEQ g−1 dry weight). As compared with the US Sediment Quality Guidelines (SQGs), the observed levels of PAHs at industrial zone docks exceeded the effects range low (ERL), and could thus cause acute biological damage. However, the lower levels of PAHs at the other zones would probably not exert adverse biological effects.  相似文献   

20.
《Marine pollution bulletin》2012,64(5-12):201-208
Flow cytometry was used to examine immune responses in haemocytes of the green-lipped mussel Perna viridis under six combinations of oxygen level (1.5 mg O2 l−1, 6.0 mg O2 l−1) and temperature (20 °C, 25 °C and 30 °C) at 24 h, 48 h, 96 h and 168 h. The mussels were then transferred to normoxic condition (6.0 mg O2 l−1) at 20 °C for further 24 h to study their recovery from the combined hypoxic and temperature stress. Esterase (Est), reactive oxygen species (ROS), lysosome content (Lyso) and phagocytosis (Pha) were reduced at high temperatures, whereas hypoxia resulted in higher haemocyte mortality (HM) and reduced phagocytosis. For HM and Pha, changes were observed after being exposed to the stresses for 96 h, whereas only a 24 h period was required for ROS and Lyso, and a 48 h one for Est. Recovery from the stresses was observed for HM and Pha but not other immune responses.  相似文献   

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