Natural and Anthropogenic Effects On Phytoplankton Primary Productivity in Mangroves

Abstract

Spatial and temporal variations and the factors influencing primary production have been studied in three different mangrove waters (Pichavaram, Ennore Creek and Adyar Estuary) of South India characterised by different anthropogenic impacts. the gross primary productivity in the unpolluted Pichavaram mangrove was 113 g Cm^?2yr^?1 exhibiting natural variability with the environmental forcing factors. Human activities have elevated primary productivity in the Ennore Creek mangrove (157g Cm^?2yr^?1) primarily through the direct discharge of fertilizer effluents. By contrast, a combination of domestic and industrial effluent discharges into the Adyar Estuary mangrove has considerably reduced phytoplankton primary productivity 83g Cm^?2yr^?1 the Redfield N: P ratio varies from 0.96 N: 1P at Ennore Creek, 1.75N: 1P at Adyar Estuary to 15.2 N: 1P at Pichavaram mangroves. This suggests that the Pichavaram mangroves represent a well equilibrated ecosystem with N: P ratio close to steady-state values in contrast to the anthropogenically altered mangrove ecosystems studied. Results show a significant temporal variability in nutrient concentration in the three mangrove areas. Distinct differences in nutrient concentrations between the dry and the wet seasons have been observed.     

The impact of enhanced ammonium sulphate inputs exceeding critical load on calluna vulgaris /peat soil microcosms

Ammonium sulphate at six concentrations in simulated precipitation has been applied weekly over two years to Calluna vulgaris growing in peat soil. The nitrogen deposition treatments were chosen to embrace and exceed critical load. The growth and composition of the Calluna and the changes over time in the chemistry of the peat soil and its soil solution were monitored. In spite of significant increases in foliar nitrogen concentration in new shoots, especially in the first year, growth did not increase significantly in response to nitrogen treatment. Several factors could be contributing to the lack of significant growth response. (1) Increasing ammonium input significantly acidified the soil solution, which could adversely effect growth directly. (2) Foliar calcium concentration was reduced significantly in both years by the ammonium sulphate treatments, and more calcium was undoubtedly lost from the rooting zone at higher nitrogen inputs. (3) Foliar phosphate declined significantly between the first and second year, so lack of growth response might also reflect a phosphorus limitation. There was a distinctly visible darkening of the leaves in response to increasing ammonium applications, especially for the first year's growth, and the chlorophyll a and b concentrations in leaves from new growth at the three highest nitrogen treatments were significantly (at P <0.05) higher than those for the control. The pigment concentrations fell markedly by the end of the second season, and treatment effects were much less consistent. It is suggested that pigment analysis therefore probably has little diagnostic value for assessing damage from pollutant nitrogen effects.     

Rare earth elements distribution in seawater and suspended particulate of the Central Mediterranean Sea

Rare earth element (REE) content in suspended and dissolved phases from the Strait of Sicily (Central Mediterranean Sea) has been measured. Vertical profiles of several dissolved REEs along the water column reflect the 3-D oceanographic features of the studied area and identifies the different water masses present there. Shale-normalized REE distribution patterns and derived parameters calculated for the suspended particulate show different atmospheric dust-surface inputs and their interactions with seawater. Finally, combined information from [La/Yb]_N, ratios, REE/La ratios and Eu anomalies measured in the suspended particulate suggest an important contribution of volcanic materials from the Etna volcano and Saharan dust to the lithogenic fraction of the suspended particulate.     

Mesoscale circulation in the surface layer off the southern and western Sardinia Island in 2000–2002

Five oceanographic cruises were organized in the Sardinian Sea and Channel in May 2000, March 2001, September 2001, May 2002, and November 2002 to study the characterization of the water masses, Atlantic Water (AW) and Winter Intermediate Water (WIW), and their mesoscale variability. In the Sardinian Channel, an Algerian anticyclonic Eddy (AE) was observed in May 2000, along the Tunisian coast. This induced a greater minimum salinity in a wider and deeper layer than in November 2002, when no AE was observed. Some WIW was observed below it; nevertheless, no link could be established between AEs and WIW occurrences. In the Sardinian Sea, two AEs were observed during spring 2000, and a further two during spring 2002. One AE strongly influenced shelf circulation, in contrast to the other three that were off the continental slope. In the same area, during the end of September 2001, a vertical salinity inversion occurred in the first 30–50 m of depth over the whole sampling field, and a W–NW wind induced a coastal upwelling over the western Sardinian coast (south of 41° N). This upwelling increased the salinity from ～20 to 30 m below the surface to the surface and, thereby led to a lower salinity close to the coast than offshore. This was in contrast to a classical upwelling. Consequently, in the Sardinian Sea, the general circulation, mainly driven by AEs, can meet the coastal wind-driven circulation.     

Composition of Floating Debris in Harbours of the United States

As part of a programme to characterize floating anthropogenic debris in the aquatic environment, the US Environmental Protection Agency (EPA) conducted 18 field surveys in the harbours of major metropolitan cities of the east, west, and Gulf coasts of the United States and the Mid-Atlantic Bight. the surveys were designed to provide information on the types, relative amounts, and distributions of aquatic debris in different geographic regions of the United States. Neuston nets (0.33 mm mesh) were used to collect surface debris during outgoing tides on two or three consecutive days in selected areas of each city. After each net tow, the debris, which ranged in size from small resin pellets to large plastic sheeting pieces, was identified, categorized, and counted. the data are being used to qualitatively characterize aquatic debris in coastal metropolitan areas, to examine potential regional variations, and to tentatively identify potential sources.     

Transport of Sewage Sludge in a Mixed Water Column

Abstract

Sewage sludge from four publicly-owned treatment works was sampled and characterized in terms of parameters affecting transport at the 106-mile deep ocean disposal site as part of the US Environmental Protection Agency's site monitoring programme. Samples from treatment plants in Passaic Valley, Rahway, and Elizabeth, New Jersey and New York City were characterized in terms of dynamic size distribution, suspended solids and density. the transport characteristics of sludge particles were measured using a 2 metre computer-interfaced laboratory settling column. Experiments were conducted at constant salinity (35 ppt) while varying hydrodynamic mixing, sludge type and concentration using a modified factorial experimental design. Hydrodynamic power dissipation was varied so that the vertical dispersion and rms fluid shear rate ranged between 0-6 cm²S^?1 and 0-30s^?1 respectively. Results indicate that at least 80% of suspended sludge particles will eventually settle under mixed conditions. the average settling velocities ranged between 0.05-4.05 × 10^-3 cm ^s-1. Shear rates above 15 s^?1 inhibited sludge settling due to aggregate breakup and boundary effects, but at a lower shear rate, differential settling and fluid shear were the dominant transport mechanisms. Sludge dilution (1/500-1/5000) had a limited effect on the settling rate. Results from this study can be used to calibrate particle transport models to determine the fate of sludge disposed at an ocean disposal site.     

Deposition Inputs,Water Quality and Liming Effectiveness

Rainfall quantity and quality, and stream and loch water quality have been monitored throughout the Loch Fleet Project. This has allowed the effects of liming of parts of the catchment to be monitored, and assessments made of the effectiveness and duration of these treatments. Rainfall over 1989–1993 fluctuated around the long-term average of 2100 mm. Over this time, year by year variations in acid or sulphate loading from deposition was evident and quite substantial. There was no trend, however, reflecting reductions in national sulphur emissions. Liming parts of the catchment in 1986 increased stream and loch water pH and calcium concentrations and reduced inorganic aluminium concentrations. Improved stream and loch water quality has been maintained for more than eight years since liming.     

Pre-and Post-Liming Aquatic Communities and Trout Diets

In the period following liming and before the introduction of brown trout to Loch Fleet, there was a reduction in the numbers of invertebrates, including the Chironomidae, Oligochaeta and Hydracarina in the loch, but an overall increase in invertebrates in the inlet and outlet streams. This was followed in the loch by a recovery in the numbers of certain groups (particularly the Trichoptera and Ephemeroptera) to pre-liming levels in spite of the introduction of the trout.

The diets of the trout comprised a wide variety of aquatic and terrestrial organisms ranging in size from Fprotozoans to newts and are dominated by chironomids. Opportunistic type of feeding as found in the present study appears to be typical of the brown trout and is reported for many water bodies by other workers.

Significant differences (P < 0.05 and P < 0.001) were found in the numbers and weights of certain food organisms in the stomachs of brown trout caught by different fishing methods in the summers of 1992 and 1993. Fish caught by gill net contained fewer planktonic crustaceans and chironomids, but greater numbers of trichopterans and terrestrial organisms, than in those caught by fly and spinner. the differences are probably related to differences in the depth at which the fish, caught by the various methods, were feeding.     

Human Influence and Classical Biogeographic Predictors of Rare Species Occurrence

Biogeographic theory predicts that rare species occur more often in larger, less‐isolated habitat patches and suggests that patch size and connectivity are positive predictors of patch quality for conservation. However, in areas substantially modified by humans, rare species may be relegated to the most isolated patches. We used data from plant surveys of 81 meadow patches in the Georgia Basin of Canada and the United States to show that presence of threatened and endangered plants was positively predicted for patches that were isolated on small islands surrounded by ocean and for patches that were isolated by surrounding forest. Neither patch size nor connectivity were positive predictors of rare species occurrence. Thus, in our study area, human influence, presumably due to disturbance or introduction of competitive non‐native species, appears to have overwhelmed classical predictors of rare species distribution, such that greater patch isolation appeared to favor presence of rare species. We suggest conservation planners consider the potential advantages of protecting geographically isolated patches in human‐modified landscapes because such patches may represent the only habitats in which rare species are likely to persist. Influencia Humana y Predictores Biogeográficos Clásicos de la Ocurrencia de Especies Raras     

Permeability of Roads to Movement of Scrubland Lizards and Small Mammals

A primary objective of road ecology is to understand and predict how roads affect connectivity of wildlife populations. Road avoidance behavior can fragment populations, whereas lack of road avoidance can result in high mortality due to wildlife‐vehicle collisions. Many small animal species focus their activities to particular microhabitats within their larger habitat. We sought to assess how different types of roads affect the movement of small vertebrates and to explore whether responses to roads may be predictable on the basis of animal life history or microhabitat preferences preferences. We tracked the movements of fluorescently marked animals at 24 sites distributed among 3 road types: low‐use dirt, low‐use secondary paved, and rural 2‐lane highway. Most data we collected were on the San Diego pocket mouse (Chaetodipus fallax), cactus mouse (Peromyscus eremicus), western fence lizard (Sceloporus occidentalis), orange‐throated whiptail (Aspidoscelis hyperythra), Dulzura kangaroo rat (Dipodomys simulans) (dirt, secondary paved), and deer mouse (Peromyscus maniculatus) (highway only). San Diego pocket mice and cactus mice moved onto dirt roads but not onto a low‐use paved road of similar width or onto the highway, indicating they avoid paved road substrate. Both lizard species moved onto the dirt and secondary paved roads but avoided the rural 2‐lane rural highway, indicating they may avoid noise, vibration, or visual disturbance from a steady flow of traffic. Kangaroo rats did not avoid the dirt or secondary paved roads. Overall, dirt and secondary roads were more permeable to species that prefer to forage or bask in open areas of their habitat, rather than under the cover of rocks or shrubs. However, all study species avoided the rural 2‐lane highway. Our results suggest that microhabitat use preferences and road substrate help predict species responses to low‐use roads, but roads with heavy traffic may deter movement of a much wider range of small animal species.