Conservation planning for connectivity across marine, freshwater, and terrestrial realms

Conservation plans are usually developed for regions that encompass only one environmental realm (terrestrial, freshwater or marine) because of logistical, institutional and political constraints. This is inadequate because these realms often interact through processes that form, utilize and maintain interfaces or connections, which are essential for the persistence of some species and ecosystem functions. We present a conceptual framework for systematic conservation prioritization that explicitly accounts for the connectivity between the terrestrial, marine, and freshwater realms. We propose a classification of this connectivity that encompasses: (1) narrow interfaces, such as riparian strips; (2) broad interfaces, such as estuaries; (3) constrained connections, such as corridors of native vegetation used by amphibians to move between natal ponds and adult habitat; and (4) diffuse connections, such as the movements of animals between breeding and feeding habitats. We use this taxonomy of inter-realm connectivity to describe existing and new spatial conservation prioritization techniques that aim to promote the persistence of processes that operate between realms.     

Linkages between atmospheric mercury deposition and the methylmercury content of marine fish

Enhanced Hg deposition to productive marine systems may result in concurrent increases in monomethyl Hg (MMHg) concentrations of marine fish. Consequently, it is important to understand what effects an increasing Hg supply may have on the marine food chain. A simple ocean model is employed to estimate the fraction of total Hg inputs which is required to sustain “average” marine fish MMHg concentrations annually. Calculations show that upwelling zones require 20% of total annual Hg inputs, coastal zones 5%, and open-ocean regions only 0.02%. The value for coastal areas is similar to that calculated for the acidified basin of Little Rock Lake, Wisconsin, a small fresh water seepage lake. These calculations point to Hg source strength and rates of particle scavenging as being key factors in controlling the rate of transport to sites of methylation (and subsequent entry into the marine food chain). If biological variables (scavenging rates, primary productivity) remain constant while anthropogenically-derived Hg deposition increases, it is likely that concentrations in marine biota (including fish) will rise in accord.     

The influence of trophic level as measured by δ15N on mercury concentrations in freshwater organisms

The relationship between mercury (Hg) concentrations in freshwater biota and trophic position, as defined by stable nitrogen isotope ratios (δ¹⁵N), was examined in 6 lakes in northwestern Ontario. The heavier isotope of nitrogen (¹⁵N) increases an average of 3 parts per thousand (‰) from prey to predator and is used as a measure of an organism's trophic position. Dorsal muscle from lake trout, burbot, walleye, northern pike, white sucker, lake cisco, lake whitefish, and yellow perch was analyzed for Hg and δ¹⁵N using flameless atomic absorption and mass spectrometry respectively. Within each lake, log Hg was significantly related to δ¹⁵N (r ² ranged from 0.47 to 0.91,P<0.01). For four species, yellow perch, northern pike, lake cisco, and lake trout, log Hg was positively related to δ¹⁵N (r ² ranged from 0.37 to 0.47,P≤0.09) across all lakes. We also used δ¹⁵N measurements (assuming a 3‰ shift between an organism and its diet) and the developed within-lake regression equations to calculate a prey Hg for each individual fish. These food Hg values were then used to predict predator Hg using Norstromet al's bioenergetics model. Predicted results were strongly correlated to measured Hg concentrations (r=0.91,P<0.001), indicating that δ¹⁵N has potential to be used in modeling.     

Mechanisms of deposition of methylmercury and mercury to coniferous forests

Deposition of methylmercury (MeHg) and mercury (Hg) to a coniferous forest have been investigated using field measurements. Samples of open field (OF) wet deposition, throughfall (TF) and litterfall (LF) have been collected and analyzed for MeHg and Hg during the period November 1991 to April 1994. Average concentrations in TF were 22.8 and 0.38 ng L^?1, for Hg and MeHg, respectively. Concentrations in OF precipitation were 11.9 and 0.37 ng L^?1, for Hg and MeHg, respectively, during the same period. Considerable differences were found for Hg in TF and OF which was attributed to a dry deposition of Hg. Hg in LF contributes a deposition of equal size as in TF. The relations between OF, TF and total Hg deposition were approximately 1∶1,5∶3. A decrease in OF Hg was found over the three year period studied. MeHg deposition in OF was also found to decrease during the same period whereas the TF MeHg showed a slight increase. Dry deposition of MeHg is also an important process in a coniferous forest although the flux to the forest floor is not via TF but rather as MeHg in LF.     

Measurement of methylmercury and mercury in run-off,lake and rain waters

During one year, samples from eight drainage lakes, seven run-off stations and three deposition sites from various geographical areas in Sweden were collected and analyzed for methyl Hg (MeHg) and total Hg (Hg-tot). The MeHg concentrations ranged from 0.04 to 0.64 ng L^?1, 0.04 to 0.8 ng L^?1, and <0.05 to 0.6 ng L^?1 in run-off, lake water and rain water, respectively. The corresponding Hg-tot concentrations were found in the range 2 to 12 ng L^?1, 1.35 to 15 ng L^?1, and 7 to 90 ng L^?1, respectively. A Hg-tot level of about 60 ng Hg L^?1 was found in throughfall water. The MeHg and Hg-tot concentrations are positively correlated in both run-off and lake water, but not in rain and throughfall water. A strong positive correlation between the MeHg, as well as the Hg-tot concentration, and the water color is observed in both run-off and lake waters, which suggests that the transport of MeHg and other Hg fractions from soil via run-off water to the lake is closely related to the transport of organic substances; and is a consequence of the biogeochemical processes and the water flow pathway. The ratio between the mean values of MeHg and Hg-tot seems to be an important parameter, with an indicated negative coupling to the mean value of pH for run-off water, but a strong positive correlation to Hg-content in fish, the ratio between the area of the catchment and the lake, as well as to the retention time of lake.     

Evaluation of sediment capping effectiveness in Hyeongsan River for in-situ management of total mercury and methylmercury contamination

Journal of Soils and Sediments - In this study, the effectiveness of in situ sediment capping was investigated as a remediation option for total mercury (THg) and methylmercury (MeHg) in the...     

Integrating freshwater and terrestrial priorities in conservation planning

The integration of freshwater and terrestrial biodiversity priorities in systematic conservation planning is a major challenge to conservation planners. Maintaining upstream–downstream connectivity and the influence of catchments on freshwater ecological integrity are some of the issues that make it difficult to reconcile terrestrial and freshwater conservation planning. As a result most conservation assessments are often biased towards terrestrial systems without adequate incorporation of freshwater biodiversity in determining priority areas for conservation. In this paper, we propose a protocol for integrating the assessment of freshwater and terrestrial priorities in conservation planning, based on a case study from Mpumalanga Province in South Africa. The approach involves the separate assessment of freshwater priority areas, and using the outcome to influence the selection of terrestrial priority areas. This allowed both freshwater and terrestrial biodiversity to be incorporated in conservation planning without compromising their unique requirements. To test the effectiveness of this approach, we assessed percentage overlap between freshwater and terrestrial priority areas, target achievement, and the area required to achieve targets. We then compared the outcome from the proposed approach with the separate assessments of freshwater and terrestrial biodiversity priorities, and when both systems are given an equal weighting in a single assessment. The results showed that there was a noticeable improvement in the overlap of priority areas for freshwater and terrestrial biodiversity from 23% to 47%. Target achievement for freshwater biodiversity improved by 10% when terrestrial assessment was based on freshwater priority areas as opposed to terrestrial systems being assessed alone. There was negligible increase in area required, whether there was integration of freshwater and terrestrial biodiversity or no integration. We conclude that the most efficient way to achieve integration in conservation planning is to preferentially select areas where freshwater and terrestrial biodiversity priorities overlap.     

Trends of mercury and methylmercury in deposition,run-off water and sediments in relation to experimental manipulations and acidification

In the covered catchment at Lake Gårdsjön, the reversibility of acidification and the effects on Hg output of a decreased deposition of Hg and MeHg have been investigated since 1991. A first indication of a decreased from the covered catchment, caused by the artificial removal of Hg and MeHg input, has been observed. This has occurred in parallel with an overall decrease in Hg deposition fluxes in SW Sweden during 1990 to 1993. In the sediments of two acidified lakes, Lake Gårdsjön (limed) and Lake Härsevatten (acid), Hg concentrations decrease by 60% in the top cm, from the maximum around 1000 ng g^–1 at 5 cm depth indicating a decreasing deposition during the last 10 years. This decrease has occurred in parallel with decreasing atmospheric S-levels and is most likely caused by decreasing European Hg emissions. Decreasing trends of MeHg in run-off from two catchments has also been observed while the Hg output has remained somewhat more stable.     

Investigation of methylmercury and total mercury contamination in mollusk samples collected from coastal sites along the Chinese Bohai Sea

This paper presents the investigation results of methylmercury and total mercury in gastropod and bivalve species collected from eight coastal sites along the Chinese Bohai Sea. The total mercury was directly determined by atomic fluorescence spectrometry (AFS), while the methylmercury was measured by a laboratory established high performance liquid chromatography-atomic fluorescence spectrometry system (HPLC-AFS). Certified reference material DORM-2 (Dogfish muscle) was used to validate the two methods and the obtained results proved to be in good agreement with the certified values. It was demonstrated that the mercury contamination was commonly existed in all selected mollusks, with methylmercury and total mercury concentration in the range of 4.8-168.4 and 6.7-453.0 ng Hg g(-)(1), respectively. Mollusks from HuLuDao were the most mercury contaminated, and those from PengLai took the second place. The species-dependent bioaccumulation capacity was observed in this study. Gastropods showed more capacity to bioaccumulate mercury than bivalves, and mercury contents in two kinds of gastropods (Rapana venosa and Neverita didyma) presented some uplifted trends with the dimensions increasing of the gastropods. Rapana venosa was found to be a potential biomarker to monitor mercury pollution in oceans. Evaluations were also made concerning about the ratio of methylmercury to total mercury.     

Multicompartment ecotoxicological models to study mercury bioaccumulation and transfer in freshwater systems

We have developed a methodology based on interactive ecotoxicological models —experimental ecosystems —, to quantify actions and interactions of abiotic and contamination factors, on bioaccumulation and transfer of Hg compounds (HgCl₂ and CH3HgCl) in freshwater systems. The first stage in the research program is based on a three compartment system : water, natural sediment and rooted macrophytes. Several abiotic factors are considered (temperature, pH, photoperiod, light intensity), in relation to two contamination sources-water column and sediment. Among the many results obtained, Hg accumulation in aquatic plants from the water source reveals small differences between the two chemical forms of the metal, the ratios between Hg concentrations in the whole plants being close to 1.5, in favor of MeHg ; after contamination by the sediment source, these ratios are higher than 20, always in favor of MeHg. Comparative study of a very large number of ecotoxicological conditions, resulting from the crossing of two or three levels for the different abiotic and contamination factors taken into account, shows important interactions, especially between pH and temperature, with reference to Hg bioaccumulation.     

Subcatchment output of mercury and methylmercury at Svartberget in northern Sweden

The subcatchments of two tributaries and the headwater mire of the 50 ha Swartberget catchment were studied. Monthly sampling was conducted during 1993 on the two tributaries and at the outlet of a mire. This was complemented by more intensive sampling during spring flood and a rain-driven episode at the end of July. Samples were analyzed for total methylmercury (MeHg), total mercury (Hg-tot) and TOC. The MeHg and TOC content of water were also fractionated into humic and non-humic components. Outputs budgets based on continuous flow monitoring and monthly volume weighted average concentrations of MeHg/ Hg were calculated for the subcatchments of the two tributaries and the mire. There was a pronounced decline in MeHg concentrations at all sampling locations during the spring flood. A clear pattern of the seasonal variation in the MeHg outputs was evident at all three sampling locations. Minimum MeHg concentrations occurred during spring flood and increased during the summer to peak levels in the autumn before tapering off during the winter (except for at the mire). The mire had larger increases in MeHg concentrations during the summer and did not decline during the winter. The warmth and increased soil humidity may promote the biogeochemical processes, including methylation, demethylation which make MeHg available for export by runoff from the soil. Variations in Hg-tot concentrations were differed from MeHg in streams that there were increases in Hg-tot concentrations with flow during both spring flood and the July rain event in runoff from the forested tributaries. The highest outputs of both humic and non-humic MeHg occurred during summer from all subcatchments. Those high outputs extended into the autumn at the mire. The largest monthly output of Hg-tot was during the spring flood period and the next largest was during the period of summer rainfall. Despite the similarity in mineralogy and atmospheric deposition on the two tributary subcatchments, there was ca 30% larger ouput of MeHg per unit area from the tributary which had deeper riparian peats. The output of Hg-tot, however, was higher on the catchment with the shallower riparian peats. The difference in the geometry of the riparian zone may contribute to these differences in output. The annual output concentrations at the mire outlet of MeHg was 0.65 ng /L and of Hg-tot was 4.04 ng/L. In the main tributary MeHg was 0.42 ng/L and Hg-tot was 3.64 ng/L. In the Västrabäcken tributary, the mean MeHg concerntration was 0.25 ng/L and the Hg-tot concerntration was 4.02 ng/L. Among the three subcatchments the largest annual output fluxes of MeHg were from the mire, 0.16 g/km2^*yr, the next from Kallkällbäcken below the mire, 0.12 g/km2^*yr, and the lowest from Västrabäcken, 0.08 g/km2^*yr.     

The detection of mutagenic pollutants in marine organisms of Kuwait

Several types of pollutants are currently entering the territorial waters of Kuwait from a variety of sources. Some pollutants, especially petrochemicals, are known to be potentially mutagenic and/or carcinogenic. Some of these chemical pollutants may enter the tissues of aquatic organisms and eventually the human body. The presence of such chemicals in the marine environment might create a serious health hazard. The marine environment of Kuwait was monitored for the presence of mutagenic chemicals using living organisms such as shrimp, clams and algae as bioindicators. These organisms were collected from selected sites within Kuwait territorial waters. Their tissues were extracted in ethanol and screened for genetically active chemicals by two standard bacterial assays, the Fluctuation Test and the Ames Test. Salmonella typhimurium TA98 was used as a tester strain. The data obtained from this study indicated that the shrimp, algae and clam samples were polluted with low concentration of frameshift mutagens. Due to the limited scope and nature of this study it was impossible to determine the source(s) of input or the chemical nature of these pollutants.     

Field sampling and analytical intercomparison for mercury and methylmercury determination in natural water

In fall 1993, two intercomparisons were conducted with laboratories performing mercury (Hg) and methylmercury (CH₃Hg) analysis in water. The first, conducted at the La Grande complex in northern Québec, involved two provincial universities and evaluated their respective sampling and analytical protocols. Some samples were spiked with a known amount of CH₃HgCl and HgCl₂ to evaluate the accuracy of the results. Samples preserved with HCl at pH<2 were analyzed up to 45 days after sampling without any change in the total Hg concentration. Filtration at the analytical lab of samples that had been previously frozen resulted in almost complete loss of Hg and CH₃Hg. It is recommended that filtration, if required, should be performed at the sampling point. The second intercomparison examined only analytical performances and included a total of seven laboratories which analyzed two samples from the Experimental Lake Area, in Northwestern Ontario. The standard deviation was 24 and 14% in total Hg for the first five labs and 31 and 21% in CH₃Hg for the first four labs. The average spike recovery in total Hg measured by three labs was 101±9%, but the two labs that performed spike recoveries on CH₃Hg obtained variable results in one case and a constant negative bias in the other case. Standard addition on all samples is recommended to assure the accuracy of CH₃Hg analysis.     

Total mercury and methylmercury mass balance in an alkaline,hypereutrophic urban lake (Onondaga Lake,NY)

A total mercury (total Hg) and methylmercury (CH₃Hg) mass balance was developed for Onondaga Lake, NY, based on sampling of tributaries, sediments, water column, and biota in 1992. Thein situ flux of total Hg and CH₃Hg from sediments to the overlying water and the rate of net CH₃Hg production in the water column were determined experimentally. Fluxes from atmospheric deposition, groundwater, and volatilization were estimated from limited field data and the literature. Ultraclean sampling and analytical techniques developed specifically for Hg were used. Results indicate that tributaries contribute the majority of total Hg entering the lake (13.6 kg in 1992). Other sources of total Hg included groundwater flux (0.02 kg), atmospheric deposition (0.44 kg), and flux from sediments (0.056 kg). Net sedimentation (11.1 kg), outflow (2.8 kg), and volatilization (0.016 kg) were sinks for total Hg. The two major sources of CH3_Hg were tributaries (0.26 kg) and net CH₃Hg production in the water column (0.60 kg). Flux from sediments accounted for only 0.017 kg CH₃Hg. Net sedimentation (0.47 kg), outflow (0.24 kg), and net uptake, by fish (0.20 kg) were sinks for CH₃Hg. Gross sedimentation of CH₃Hg exceeded net sedimentation by 90%, suggesting that release of CH₃Hg from settling particles is a significant process.     

Sulfur and iron influence the transformation and accumulation of mercury and methylmercury in the soil-rice system

Journal of Soils and Sediments - Much attention is directed to the accumulation of mercury and methylmercury (MeHg) in rice grown on Hg-contaminated paddy fields, since they pose a risk to the...     

A case study of mercury and methylmercury dynamics in a Hg-contaminated municipal wastewater treatment plant

A study of total Hg (Hg) and methylmercury (MeHg) was performed in a 40 mgd capacity municipal sewage treatment plant in which elemental Hg was used as a seal in 3 trickling filter center columns. Each seal contains several hundred kg of Hg. The seals have leaked repeatedly over time, prompting the current remediation study and ongoing replacement of the Hg seals with mechanical seals. A mass balance conducted three times while the seals were in place showed that the plant acted as a net source of both Hg and MeHg during normal operation. The average amount of Hg released in sludge plus effluent was 157 g Hg and 0.4g MeHg/d. Of this total, 138 g Hg and 0.3 g MeHg were in excess of influent wastewater, and were contributed by the WTP itself. About 95% of the total Hg was released in sludge, with only 6 to 7 g/d released to the receiving water body. However, on average, about 70% of the MeHg leaving the plant was released to the river. Effluent MeHg concentrations were 4–6 ng/L. The plant components that acted as the major sources of both total and MeHg within the plant were the trickling filters (TFs). Metallic Hg accidentally lost from the center column seals has accumulated in the rock filter media and underbedding of the tricking filters. MeHg production across the TFs was positively related to the Hg concentration in each of the TFs. A substantial fraction of the total Hg but not of MeHg was lost to sludge in each settling step. About 50% of the remaining MeHg appeared to be degraded during the tertiary aeration step.     

The profile distribution of total and extractable zinc in selected Nigerian soils

Abstract

The profile distribution of total, DTPA‐ and 0.1 N HC1‐extractable Zn was determined in 11 Nigerian soil profiles formed on various parent Materials including the coastal plain sands, shales, basalt, granite and banded gneiss.

The total content ranged from 9 to 84 ppm. Generally soils developed on igneous rocks contained more Zn than those on sedimenatary deposits. Among the soils on sedimentary rocks, those on shale had more total Zn than those on sandstones. Total Zn was weakly correlated with organic matter but strongly associated vith clay content and free oxides of iron and manganese.

The amounts of Zn extracted by DTPA and 0.1 N HC1 ranged from 0.01 to 10.98 and from 0.23 to 6.25 ppm, respectively. The dilute acid generally removed more Zn from the soils than did the DTPA. The amounts extracted generally decreased vith depth especially vith DTFA extractant. Soils developed on basalt and shales contained the highest amounts of 0.1 N HCl‐extractable Zn while those on basement complex rocks gave the highest values of DTPA‐extractable Zn. Extractable Zn from soils on coastal plain sands remained relatively lev. The extractable Zn was more associated vith organic matter than vith clay content.     

The profile distribution of total and extractable copper in selected Nigerian soils

Abstract

The profile distribution of total, DTPA‐ and 0.1N HCl‐extractable Cu was determined in 11 Nigerian soil profiles formed from various parent materials including the coastal plain sands, shales, basalt, granite and banded gneiss.

Total Cu ranged from 7 to 72 ppm with a mean of 35 ppm₀ The soils formed from basalt had the highest values while those on coastal plains had the least content. Generally, there was a higher content in the subsoils than in the surface horizons. The total Cu significantly correlated with percent clay and the free oxide contents of Fe and Mn.

DTPA ‐ and 0.1N HCl‐extractable Cu ranged from 0.08 to 2.81 ppm and 0.10 to 7.78 ppm, respectively. Soils on metamorphic rocks gave the highest values of DTPA‐extractable Cu. The DTPA‐extractable Cu ‐was only related to pH but the acid extractable Cu was associated with total Cu, clay, free Fe₂O₃ and MnO₂ contents.