CO2 Efflux from Shrimp Ponds in Indonesia

The conversion of mangrove forest to aquaculture ponds has been increasing in recent decades. One of major concerns of this habitat loss is the release of stored ‘blue’ carbon from mangrove soils to the atmosphere. In this study, we assessed carbon dioxide (CO₂) efflux from soil in intensive shrimp ponds in Bali, Indonesia. We measured CO₂ efflux from the floors and walls of shrimp ponds. Rates of CO₂ efflux within shrimp ponds were 4.37 kg CO₂ m⁻² y⁻¹ from the walls and 1.60 kg CO₂ m⁻² y⁻¹ from the floors. Combining our findings with published data of aquaculture land use in Indonesia, we estimated that shrimp ponds in this region result in CO₂ emissions to the atmosphere between 5.76 and 13.95 Tg y⁻¹. The results indicate that conversion of mangrove forests to aquaculture ponds contributes to greenhouse gas emissions that are comparable to peat forest conversion to other land uses in Indonesia. Higher magnitudes of CO₂ emission may be released to atmosphere where ponds are constructed in newly cleared mangrove forests. This study indicates the need for incentives that can meet the target of aquaculture industry without expanding the converted mangrove areas, which will lead to increased CO₂ released to atmosphere.     

Shrimp ponds lead to massive loss of soil carbon and greenhouse gas emissions in northeastern Brazilian mangroves

Mangroves of the semiarid Caatinga region of northeastern Brazil are being rapidly converted to shrimp pond aquaculture. To determine ecosystem carbon stocks and potential greenhouse gas emissions from this widespread land use, we measured carbon stocks of eight mangrove forests and three shrimp ponds in the Acaraú and Jaguaribe watersheds in Ceará state, Brazil. The shrimp ponds were paired with adjacent intact mangroves to ascertain carbon losses and potential emissions from land conversion. The mean total ecosystem carbon stock of mangroves in this semiarid tropical landscape was 413 ± 94 Mg C/ha. There were highly significant differences in the ecosystem carbon stocks between the two sampled estuaries suggesting caution when extrapolating carbon stock across different estuaries even in the same landscape. Conversion of mangroves to shrimp ponds resulted in losses of 58%–82% of the ecosystem carbon stocks. The mean potential emissions arising from mangrove conversion to shrimp ponds was 1,390 Mg CO₂e/ha. Carbon losses were largely from soils which accounted for 81% of the total emission. Losses from soils >100 cm in depth accounted for 33% of the total ecosystem carbon loss. Soil carbon losses from shrimp pond conversion are equivalent to about 182 years of soil carbon accumulation. Losses from mangrove conversion are about 10‐fold greater than emissions from conversion of upland tropical dry forest in the Brazilian Caatinga underscoring the potential value for their inclusion in climate change mitigation activities.     

盐碱地渗水盐度与钠钾比对凡纳滨对虾生长的影响

为广泛利用滨海盐碱地渗水开展对虾养殖,本文研究了盐碱地渗水不同盐度及钠钾比（Na⁺/ K⁺）对凡纳滨对虾存活、生长、代谢及体内谷草转氨酶（GOT）、谷丙转氨酶（GPT）和Na⁺-K⁺-ATPase等3种酶活性的影响.试验用水盐度分别为5、10和15,各盐度组Na⁺/K⁺分别为20、40、50、60、70和90,试验周期为20 d.结果表明,盐度为15的条件下,凡纳滨对虾的存活、生长、代谢及酶活性表现最佳,在此盐度条件下,Na⁺/K⁺保持在40和50条件下,凡纳滨对虾存活、生长、代谢及酶活力较高.表明盐碱地渗水经适当调配可用于凡纳滨对虾的养殖.     

Challenges of a transition to a sustainably managed shrimp culture agro-ecosystem in the Mahakam delta,East Kalimantan,Indonesia

Around 1990, when in other countries mangrove protection took off, massive conversion of mangrove forest into shrimp ponds started in the Mahakam delta. To identify constraints to and options for sustainable management we analysed institutions and constraints with stakeholders. In 3 sites we used participatory tools and a complementary survey to assess the livelihood framework. Since 1970, ponds for shrimp farming gradually replaced 75% of mangrove forested area. After 2004, recovery of mangrove took off, as, mainly due to low shrimp yields, ponds were abandoned. In 2008, 54% of the delta was dedicated to ponds for shrimp production. Around 80% of livelihood activities of pond-farmers, pond caretakers, and fishermen was related to mangroves. The involvement of men and women in these activities varied between sites and types. Poor households depended more on mangroves. Most activities resulted in seasonal income peaks; only a few activities resulted in a full daily livelihood. Ponds, on the other hand, provide 50% of households’ livelihood, but this remains vulnerable in the context of the risky shrimp production. Skewed land holding, unequal sharing of benefits, competing claims and vested interests of stakeholders pose a great challenge to a transition to a more sustainable use of the mangrove area. In particular, ponds located on peat soils are non-sustainable and would require full restoration into mangrove; ponds on other soils could best be transformed into a mixed mangrove-pond system using a ‘green-water’ technology.     

Effects of soil pH and calcium on mycorrhizas of Picea abies

The effects of lime, increased soil pH and increased soil Ca concentration on the mycorrhizas of Norway spruce. [Picea abies (L.) Karst.] were studied independently of each other to elucidate the different mechanisms through which lime may influence mycorrhizas in acidic soil. In a field experiment (mature Norway spruce in podzol), lime was applied as CaCO₃; increased Ca concentration without an increase in pH was achieved with CaSO₄; and soil pH was increased without calcium by means of Na₂CO₃ and K₂CO₃ (Na+K treatment). Treatments were done in October, and mycorrhizas were counted from samples collected in the following June and September. All treatments increased the percentage of dead short root tips compared to controls in September, and Na+K already in June. Cenococcum geophilum Fr. increased in proportion in plots treated with Na+K.In a sand culture experiment, Norway spruce seedlings were grown from seed and inoculated with Cenococcum geophilum, or root inoculum, or left uninoculated. When mycorrhizas were beginning to form, CaCO₃ and CaSO₄ treatments were applied. Six weeks later, the percent of dead short root tips in both salt treatments was significantly increased from control, but formation of mycorrhizas was not inhibited by treatments.As all the treatments increased the proportion of dead short root tips, it is concluded that lime directly and adversely affected mycorrhizas of Norway spruce in sand culture and in mor humus. Both increased ionic strength and increased pH may be reasons for this rather than Ca²⁺ specifically.     

Influence of roots and climate on mineral and trace element storage and flux in tropical mangrove soils

The storage and flux of various mineral and trace elements in soils (0–30cm depth) were examined in relation to monsoonal rains and fine root biomass in four mangrove forests of different age and type in southern Thailand. The onset of the wet SW monsoon resulted in the percolation and dilution of porewater solutes by rainwater and by less saline tidal water, as indicated by shifts in Eh, pH and porewater SO₄/Cl ratios. This is contrary to temperate intertidal environments where seasonal patterns of porewater constituents, and biological and biogeochemical activities, are strongly cued to temperature. Fluxes across the soil–water interface were most often not statistically significant. Concentration of dissolved porewater metals were dominated by Fe, Mn, Al, Mo and Zn. The decreasing order of solid-phase element inventories in these soils, on average, was: Al, S, Fe, Na, Mg, K, Ca, N, P, Mn, V, Zn, Cr, Ni, As, Co, Cu, Pb, Mo, Cd and Hg. There were no gradients in concentrations of dissolved or solid-phase elements with increasing soil depth. This phenomenon was attributed to physical and biological processes, including the presence and activities of roots and tidal recharge of soil water. Fine dead roots were storage sites for most mineral and trace elements, as some elements in roots composed a significant fraction (5%) of the total soil pool. Analysis of S and Fe concentration differences between live and dead roots suggested extensive formation of pyrite associated with dead roots; correlation analysis suggested that trace metals coprecipitated with pyrite. An analysis of inventories and release/uptake rates indicate turnover of the N, P, Na and Ca soil pools equivalent to other tropical forests; turnover was slow (decades to centuries) for S, Fe, K and trace elements. Our results indicate that mineral and trace element cycling in these soils are characterized by net storage, with net accumulation of most elements much greater than uptake and release by tree roots.     

南美白对虾淡化养殖对周边环境盐碱化的影响分析

为探讨淡化养殖南美白对虾(Penaeus vannamei)对养殖区周边环境盐碱化的影响, 本研究对湖南澧县南美白对虾淡化养殖1年、3年、5年和7年的池塘及排水沟渠附近底泥样品进行了钾、钙、镁、钠、水溶性盐总量、氯离子等土壤盐碱化指标分析。结果显示, 养殖池塘水溶性总盐含量均高于对照组。对比对照组, 养殖池塘沉积物的氯离子浓度随养殖年份显著增加, 5年的池塘Cl-含量最高。养殖池塘中Na+、K+浓度与对照组相比无差异, 到第7年Na+显著增加。养殖池塘沉积物中Mg2+、Ca2+浓度对比对照组显著下降, 养殖7年池塘Mg2+浓度与对照池塘相近, 而7年的池塘Ca2+浓度显著高于对照组。结果表明, 随着养殖年份的递增, 养殖池塘的总盐、氯离子、Na+和Ca2+等盐碱化指标会呈现一定上升趋势, 但目前整体未出现超出正常土壤标准状况, 具体影响需进一步跟踪监测。     

<Emphasis Type="Italic">Daphnia galeata</Emphasis> in the deep hypolimnion: spatial differentiation of a “typical epilimnetic” species

One of the most serious threats to tropical mangrove ecosystems caused by shrimp farming activities is the poor management of pond waste materials. We hypothesise that mangroves can tolerate chemical residues discharged from shrimp farms and can be used as biofilters, but the capability of mangroves to cope with solid sediments dredged from shrimp ponds is limited. Our study in Pak Phanang, Thailand, confirmed that the excess sediments discharged from nearby shrimp ponds reduced mangrove growth rates and increased mortality rates. A series of transformed multi-temporal satellite images was used in combination with the field data to support this claim. In addition, a comparison between four dominant mangrove species revealed that Avicennia marina could tolerate sedimentation rates of >6 cm year⁻¹, while Bruguiera cylindrica tolerated sedimentation rates of 5 cm year⁻¹ (total sediment depth = 25 cm) before dying, while Excoecaria agallocha and Lumnitzera racemosa performed intermediate. This outcome implied that in our situation A. marina and to lesser extent E. agallocha and L. racemosa could be more effective as biofilters than B. cylindrica, as they may survive the sedimentation longer in the disposal areas. Further studies on the impact of sedimentation and chemical pollution of shrimp farm wastes on mangrove mortality and growth are required.     

Effects of Ledum groenlandicum amendments on soil characteristics and black spruce seedling growth

The effects of leaves and litter of the boreal forest understory shrub, Ledum groenlandicum, on soil characteristics and black spruce (Picea mariana) seedling growth were investigated. Organic and mineral soils, not previously associated with L. groenlandicum, were amended with leaves and litter of this species. The objectives of the present study were: (i) to determine the changes in soil characteristics after amending with L. groenlandicum, (ii) to determine the quantitative variation in the concentration of water-soluble phenolic allelochemicals in mineral and organic soil layers modified by L. groenlandicum and (iii) to study the growth response of black spruce in soils treated with different L. groenlandicum amendments. The amended organic and mineral soils were analyzed for pH, organic matter, PO₄, N, Ba, Cu, Zn, Fe, Mn, Ca, Na, K, Mg, Al and total phenolics equivalence. Results indicate that organic soils amended with L. groenlandicum leaves and litter were significantly different from unamended control soil for most of the chemical characteristics, while amended mineral soil was different from that of unmodified mineral soil for PO₄, organic matter, K and total phenolics equivalence. Water-soluble phenolics from L. groenlandicum and changes in nutrient availability are plausible causes of L. groenlandicum interference with black spruce seedling growth.     

The chemistry of surface water in prairie ponds

Water analyses from 80 small prairie ponds, 0.17 to 89.8 hectares, in Manitoba and Saskatchewan between 1967 to 1972 exhibited two basic ionic dominance patterns HCO₃ > SO₄ > Cl and SO₄ > HCO₃ > Cl. The order of SO₄ and Cl were reversed in 40 percent of the bicarbonate ponds below 500 µmhos/cm. At salinities above 12,000 µmhos/cm, Cl exceeds SO₄ in several wetlands. Temporary wetlands were characterised by Ca > K > Mg > Na / HCO₃ > Cl > SO₄, semi-permanent ponds Mg > Ca > Na > K / SO₄ > HCO₃ > Cl while the permanent pond structure was Ca > Mg > Na > K / HCO₃ > SO₄ > Cl.Conductivities of the wetlands studied ranged from 47 to 23,000 µmhos / cm.Seasonal changes in salinity varied within and between pond types as well as from year to year. The average salinity increase within season in temporary ponds was 67 percent, 63 percent in semi-permanent ponds and 20 percent for permanent ponds. These changes were affected by evaporation, transpiration, see-page and precipitation patterns. Ionic dominance patterns did not change within a season although Mg, K and HCO₃ increased at higher rates than Ca, Na, CI and SO₄.Temporary wetlands are slightly acidic, averaging pH 6.8 while semi-permanent and permanent ponds were alkaline, pH range 7.1 to 9.2. No stratification of pH with depth and minimal diurnal variation was recorded.At two study areas, Bradwell and St. Denis fhe following ranges (micrograms/litre) were recorded: 3 to 630 PO₄-P, 10 to 650 NO₃-N, 5 to 630 TDFe, 1 to 13 TDCu and 1 to 27 TDZn. Colour was 5 to 190 Hazen units at St. Denis and 10 to 110 for Bradwell.Two herbicides, 2,4-D and 2,4,5-T were detected at levels of 4 to 111 and 1.4 to 13.5 micrograms/litre, respectively, from 15 ponds at St. Denis.     

Mangroves and brackishwater pond culture in the Philippines

Around 50% of mangrove loss in the Philippines can be traced to brackishwater pond construction. The decrease in mangroves from 450 000 ha in 1920 to 132 500 ha in 1990 has been accompanied by expansion of culture ponds to 223 000 ha in 1990. The history of fishpond development in the country includes a government-sponsored fishpond boom in the 1950-g and 1960s, the proconservation decade of the 1970s followed by a shrimp fever in the 1980s. Production from brackisshwater ponds has increased from 15 900 mt worth P7.6 million in 1938 to 267 000 mt valued at P6.5 billion in 1990. On the other hand, the maximum valuation of over $11 000 ha^–1 yr^–1 for unmanaged and managed mangrove forests makes them economically on par with the most profitable pond farming systems. The loss of mangrove systems and their varied goods and services is the single most important consequence of brackishwater pond culture in the Philippines. Moreover, intensive shrimp farming is associated with other ecological and socioeconomic effects such as pollution of coastal waters and decline in domestic food crops. New legislation and enforcement of existing laws, conservation of remaining mangroves, massive rehabilitation of denuded mangrove areas, and promotion of sustainable aquaculture and fisheries are recommended.     

Mangroves as filters of shrimp pond effluent: predictions and biogeochemical research needs

Preliminary estimates of the ratio of mangrove forest: shrimp pond area necessary to remove nutrients from shrimp pond effluent are made using budgets of nitrogen and phosphorus output for semi-intensive and intensive shrimp ponds combined with estimates of total net primary production in Rhizophora-dominated mangrove forests in tropical coastal areas. If effluent is delivered directly to mangrove forest plots, it is estimated that, depending on shrimp pond management, between 2 and 22 hectares of forest are required to filter the nitrogen and phosphorus loads from effluent produced by a 1 hectare pond. While such ratios may apply to small scale, integrated shrimp aquaculture — mangrove forestry farming systems, the variability in mangrove hydrodynamics makes it difficult to apply such ratios at a regional scale. Before mangroves can be used to strip shrimp pond effluent more research is required on the effects that high ammonia and particulate organic matter loads in pond effluent have on nutrient transformations in mangrove sediments and on forest growth.     

Longevity of simultaneous operation of aquaculture and mangrove forestry as explained in terms of water and sediment qualities

A silvofishery system (SFS) of 5.2 ha, simultaneously combining aquaculture (shrimp, crab, and fish) and forestry, was studied to understand how the water/sediment qualities had remained viable for 30 years. The long life of this SFS pond contrasts sharply with a short life of many conventional, intensively managed shrimp ponds (5 years on average). Total ammonia nitrogen in the SFS water (0.06 mg l^?1) was much lower than the Thai environmental safety standard for shrimp ponds (1.0 mg l^?1) and approximately 0.05 % of an average conventional, intensively managed shrimp pond. Total organic nitrogen of the pond sediment was 1.47 mg g^?1 which was almost half of conventional, intensively managed shrimp ponds. The flux study revealed that NH₄–N was the dominant form of nitrogen, with lesser amounts of NO₂–N and NO₃–N, and that NH₄–N was being released from the sediment into the water. Nitrogen loss from the pond, which was regarded as the denitrification rate, was estimated to be 71.5 mgN m^?2 d^?1, corresponded to 55 % of the total nitrogen input. As the average denitrification rate in a conventional, intensively managed shrimp pond is 13.4 %, the SFS was shown to be relatively efficient in removing accumulated nitrogen from the pond. Assuming accepted feed conversion rates, 3,340 kg of feed would have been necessary for the amount of fishery production recorded during 5 May 2005 and 22 March 2006. However, only 380 kg of trash fish was added, representing a saving of 2,960 kg of feed. Such a saving could be attributed to detritus from the mangrove trees that have been growing within the pond and algae encouraged to bloom by the shallow water depth. Therefore, it is suggested that the efficient nitrogen removal due to the high denitrification rate as well as the reduced feed input from mangrove detritus substitution, have contributed to maintaining favourable water and sediment qualities, resulting in the longevity of SFS pond.     

Including GHG emissions from mangrove forests LULUC in LCA: a case study on shrimp farming in the Mekong Delta,Vietnam

Purpose

Mangrove forests have been recognized as important regulators of greenhouse gases (GHGs), yet the resulting land use and land-use change (LULUC) emissions have rarely been accounted for in life cycle assessment (LCA) studies. The present study therefore presents up-to-date estimates for GHG emissions from mangrove LULUC and applies them to a case study of shrimp farming in Vietnam.

Methods

To estimate the global warming impacts of mangrove LULUC, a combination of the International Panel for Climate Change (IPCC) guidelines, the Net Committed Emissions, and the Missed Potential Carbon Sink method were used. A literature review was then conducted to characterize the most critical parameters for calculating carbon losses, missed sequestration, methane fluxes, and dinitrogen monoxide emissions.

Results and discussion

Our estimated LUC emissions from mangrove deforestation resulted in 124 t CO₂ ha^?1 year^?1, assuming IPCC’s recommendations of 1 m of soil loss, and 96% carbon oxidation. In addition to this, 1.25 t of carbon would no longer be sequestered annually. Discounted over 20 years, this resulted in total LULUC emissions of 129 t CO₂ ha^?1 year^?1 (CV = 0.441, lognormal distribution (ln)). Shrimp farms in the Mekong Delta, however, can today operate for 50 years or more, but are 1.5 m deep (50% oxidation). In addition to this, Asian tiger shrimp farming in mixed mangrove concurrent farms (the only type of shrimp farm that resulted in mangrove deforestation since 2000 in our case study) resulted in 533 kg methane and 1.67 kg dinitrogen monoxide per hectare annually. Consequently, the LULUC GHG emissions resulted in 184 and 282 t CO₂-eq t^?1 live shrimp at farm gate, using mass and economic allocation, respectively. These GHG emissions are about an order of magnitude higher than from semi-intensive or intensive shrimp farming systems. Limitations in data quality and quantity also led us to quantify the uncertainties around our emission estimates, resulting in a CV of between 0.4 and 0.5.

Conclusions

Our results reinforce the urgency of conserving mangrove forests and the need to quantify uncertainties around LULUC emissions. It also questions mixed mangrove concurrent shrimp farming, where partial removal of mangrove forests is endorsed based upon the benefits of partial mangrove conservation and maintenance of certain ecosystem services. While we recognize that these activities limit the chances of complete removal, our estimates show that large GHG emissions from mangrove LULUC question the sustainability of this type of shrimp farming, especially since mixed mangrove farming only provide 5% of all farmed shrimp produced in Vietnam.

     

Rhizophora Mangrove Agroforestry

Conversion of mangrove forests for fish and shrimp ponds has been occurring in South Sulawesi, Indonesia for more than half a century. In some communities virtually all mangrove forest has been removed and subsequent environmental consequences have been encountered, including flooding and coastal erosion. One group of communities has countered negative environmental impacts, while at the same time increasing their incomes, through development of a mangrove agroforestry system. Monocultural plantings ofRhizophora mucronata Lam. in blocks along the coast have mitigated erosion and reduced flooding, protecting fish and shrimp ponds located inland. Controlled harvesting of the planted trees has produced sizeable incomes through fuelwood sales.     

Performance of WSSV-infected and WSSV-negative Penaeus monodon postlarvae in culture ponds.

In a survey of 27 Penaeus monodon culture ponds stocked with postlarvae (approximately PL10) at medium density (approximately 40 shrimp m(-2)), single-step nested white spot syndrome virus (WSSV) PCR was used to measure the WSSV infection rates in the shrimp populations within 1 mo after stocking. Seven ponds were initially WSSV-free, and the shrimp in 5 of these were harvested successfully. In the ponds (n = 6) where detection rates were higher than 50%, mass mortality occurred during the growth period, and none of these ponds was harvested successfully. In a subsequent study, P. monodon brooders were classified into 3 groups according to their WSSV infection status before and after spawning: brooders that were WSSV-positive before spawning were assigned to group A; spawners that became WSSV-positive only after spawning were assigned to group B; and group C consisted of brooders that were still WSSV-negative after spawning. WSSV screening showed that 75, 44 and 14%, respectively, of group A, B and C brooders produced nauplii that were WSSV-positive. Most (57%; 16/28) of the brooders in group A produced nauplii in which the WSSV prevalence was high (>50%).When a pond was stocked with high-prevalence nauplii from 1 of these group A brooders, an outbreak of white spot syndrome occurred within 3 wk and only approximately 20% of the initial population survived through to harvest (after 174 d). By contrast, 2 other ponds stocked with low-prevalence and WSSV-negative nauplii (derived respectively from 2 brooders in group B), both had much higher survival rates (70 to 80%) and yielded much larger (approximately 3x by weight) total harvests. We conclude that testing the nauplii is an effective and practical screening strategy for commercially cultured P. monodon.     

Effects of liming on soil chemical characteristics and grass growth in laboratory and long-term field-amended soils

Summary The influence of liming on soil solution composition was compared in two laboratory amended soils and one field amended soil. In the laboratory study, soil solutions were sampled by miscible displacement at intervals of 1 and 10 weeks after liming. In addition to increases in pH and Ca, there were large reductions in the concentrations of Mg, K, Na, Si and Mn. Solution concentration of free Al decreased with liming; however, organically complexed Al increased, as did soluble organic matter. Liming also stimulated mineralization of N as indicated by increased solution NO₃ levels. The field amended soils were obtained from a long-term cutting trial investigating the effects of lime on pasture. Despite the passage of a 16-year interval since application, the effects of lime on soil solution characteristics were still clearly evident and generally consistent with those observed in the laboratory study. Estimated leaching losses of Ca from limed soil were relatively low, amounting to 12%, 27% and 44% of the 4.2, 8.4 and 12.5 t lime ha⁻¹ applied, respectively. The results suggest that, in Eastern Ireland, a lime treatment would maintain and elevated pH and would influence the avialability and mobility of plant nutrients for some decades following application.     

Membrane potentials, electrolyte contents, cell pH, and some enzyme activities of fibroblasts

The resting membrane potential of the cultured fibroblasts derived from rabbit subcutaneous tissues was -10.2 +/- 0.20 mV (n = 390). This potential was affected by the potassium concentration in the culture medium, but not by other chemical or hormonal preparations, such as dibutyryladenosine 3',5'-cyclic monophosphate (0.5 to 5.0 mmol/l), sodium fluoride (10(-5) to 10(-4) M), hydrocortisone (10(-7) to 10(-6) M), parathyroid extract (0.5 to 1.0 U/ml), or thyrotrophin (5 to 10 mU/ml). The Na+, K+, and Cl- concentrations of the cultured fibroblasts were 35.4, 85.7, and 22.6 mmol/l cell water, respectively. The water and protein contents of these cells were 82.1 and 9.18 g/100-g cells, respectively. The intracellular pH of fibroblasts as determined by [14C] dimethyloxazolidine-2, 4-dione, and 3H2O ranged between 6.9 and 7.1 when the pH of the culture medium was maintained at 7.4. The activities of Na+, K+-, HCO3(-)-, and Ca++, Mg++-ATPases in these cultured cells were 19.0 +/- 2.1, 13.6 +/- 2.1, and 6.6 +/- 1.2 nmol pi/mg protein per minute, respectively, and the carbonic anhydrase activity was 0.054 U/mg protein. Calculations based on the values for the membrane potential and the electrolyte concentrations observed in this study indicate that Na+, K+, Cl-, and H+ are not distributed according to their electrochemical gradients across the cell membrane. Na+, Cl-, and H+ are actively transported out of the cells and K+ into the cells.     

亚热带河口陆基养虾塘水体溶解性碳浓度及沉积物-水界面碳通量时空动态特征

以福建闽江和九龙江河口陆基养虾塘为研究对象,通过野外原位观测和室内模拟培养实验,开展了河口陆基养虾塘养殖期间水体溶解性有机碳(DOC)和溶解性无机碳(DIC)及养虾塘沉积物-水界面碳交换通量变化特征的研究。结果表明:时间变化上,养虾塘水体溶解性碳浓度及沉积物-水界面碳通量在闽江河口呈现8月中旬10月中旬6月中旬的特征,在九龙江河口表现为随养殖阶段推移而增加的趋势;空间变化上,闽江河口养虾塘水体溶解性碳浓度及沉积物-水界面碳通量显著高于九龙江河口;沉积物释放溶解性碳速率与水体溶解性碳浓度呈现显著正相关关系,沉积物碳释放过程是引起养虾塘水体溶解性碳浓度时空变化的重要因素。表明河口区水产养虾塘碳循环研究时需考虑不同形态碳生物地球化学循环的时空差异性。