Study of density, distribution and yield on benthic fauna and brown trout (Salmo trutta fario) feeding in Laar reservoirs

Lar lake, with the international UTM specification of 39S 579680 3976567 & 39S 589930 3976184 is Situated in Lar national Park with an aerial distance of 55 Km of Tehran along Haraz road. The present research is carried out as part of a comprehensives Plan for assessment of bioresearches of Lar lake & the rivers flowing into it. This research includes examination of there benthic Samplings performed in Lar lake and each of the related rivers including Delichaee, Ab-e-sefid , Alarm & Lar (Kamardasht).Tubifex and Chironomus genus were found to have the highest frequencies of occurrence in the lake with %77.117 & %21.823 respectively followed by Chironomidae and Simulidae from the Diptera order which accounted for %72.328 and %13.812 occurrences in four rivers examined in the Study. The benthic biomass at various examined Sites and the average wet weight of the benthic biomass in station No one in the lake Was 17.397g and the figure for the examined site in Alarm was 20.242 g which were the highest level among Other examination stations the index for the abundance of species in Alarm river was greater than the rest of the examined rivers with 12.57. A sum of 354 Pieces of brown trouts was caught in the course of sampling which were closely investigated in terms of their digestive tract Content. It was identified that Daphniidae and Chironomus constituted the bulk of eaten items from the lake with %17.985 and %63.973 respectively. Meanwhile, Chironomidae and Simuladae were the most frequently eanten benthos by the fish with %81.47 and %7.93 respectively.The index for the relative length of gut was recorded at 0.49± 0.08 which is well indicative of the carnivorous diet of the fish.The index for the feeding intensity amounted to 138  83 showing that the one year old fish were of more feeding intensity.The coefficient of condition (K) was estimated at 1.02  0.142 for all the caught fish. The average wet weight of the benthos was 10.348 g per square meter which if extended to 700ha surface area of the lake, the total macrobenthic production in the lake would amount to 72730Kg of wet weight or 6510 Kg of dry weight. Since the Secondary Production of macrobenthos have always been double that of their biomass, it is reasonable to assume that the Secondary Production of macrobenthos amount to 145640 Kg by their wet weight and Since the energy transfer in the food chain of the lake from benthos to fish is 10 percent, the fish production Capacity Coming from benthic resources of the lake (Lar) would be 14.5 MT, half of which (7000-8000MT) could annually be harvested. Further more, the actual fish Production Capacity might exceed the projected level Since Daphnia, Rotifers and Ostracoda which belong to Zooplanktons, play a part in the natural diet of trout. Meanwhile, rivers Play a major role in fish nutrition and the annual fish production in Delichaee river is about 4481.8Kg while the figures for Ab-e-sefid, Alerm and Lar rivers are 2370.7 4848.7 and 2586.2 Kg respectively, that further increase fish Production in the area and every year half of these resources can be exploitable from the river & the lake.Nevertheless, due to ecological & biological importance of rivers and the probability of environmental Pollution, devastation of natural fish habitats & their nursery grounds, Sport fishing is not recommended at all.

Benthic fauna and water quality in Gorganrood River, Iran

This present work study on water quality and benthic Macro invertebrate in Gorganrood, river. The research was carried out at 6 sampling site and the abundance and diversity of benthos were monitored along the length of river between 2007_2008_14 families were recorded in phyla, namely Annelidae, Mollusca,.... The greatest number of species was at 1 st station and the least number was at 6th station. The upper section supported more diverse community then the lower section. A low macro invertebrate abundance was observed during spring as a result of heavy rainfall and flood, and generally in all lowest section because of high valve of nitrogen and other nutrients. Water physiochemical parameters such as Phosphate, Nitrate,TPS and others were measured and water quality were studied through different indices such as saprobic system, Helsinhoff (FBI), BMWP and the results were compared and evaluated by physical chemical and parameters. The result indicated that the water quality in the up stream and the middle were good to fair, but the down stream qualities were pour at all sites.

The study of ecological condition on productivity of Tajan River estuary in Mazandaran Province Caspian Sea

This project was done during a one-year period (2006-2007) with the aim of assessing and evaluating the susceptible and vulnerable habitat of Tajan River estuarine region as well as identifying its ecological features. This region consists of Tajan estuarine region as one of the sub-basins of the Caspian Sea basin which covers a surface of 2km2. In this assessment, 6 riverine estuarine and marine stations were chosen in which non-biotic parameters such as temperature, salinity, dissolved oxygen, pH and nutrients, and biotic parameters such as variation, density, plankton, primary production by chlorophyll-a. Benthos variation density, silt and the organic materials of the sediments were sampled and measured monthly. The amount of chlorophyll-a concentration and primary production showed a lot of seasonal changes at these stations which ranged from0.3 to 96 mg/m3. The results from the primary productions indicated that the eastern station of the estuary had high concentrations of chlorophyll-a during all seasons (96mg/m3). The most important and dominant planktonic groups in this region included Bacillariophyta from plankton and copepoda from zooplankton. The most important Benthos communities consisted of Driessena polymorpha.Cerastoderma lamarki in estuarine region,Chironomus plumosus in riverine region and Hypaniola sp. In marine region. Assessing the annual variation in these three riverine, estuarine and marine regions, phytoplankton with 3.1, Zooplankton with 2.7 and Benthos with 1.9 Showed the most density in the estuarine region. Assessing the annual density, phytoplanktonic (6118967 no . in m3) and zooplanktonic (7272 no . in m3) communities showed the most density in the marine region. Assessing the statistical tests showed that the estuarine and riverine regions had a significant difference in planktonic density (p<0.005) compared with the marine region. Moreover, The zeoplanktonic density in the marine region had a significant difference (p<0.005) with estuarine and riverine regions. Tooki test and one-way variance Analysis showed that in assessing the planktonic groups (p<0.005) and Benthos (p<0.005), there was a significant difference in variation index between river with estuary, and estuary with the sea. The amount of the total annual live biomass of the Benthos resource in Tajan river estuarine region was estimated 757.66 g/m2.

Effects of cage fish culture on water quality and selected biological communities in northern Lake Victoria, Uganda

Growing of fish in cages is currently practiced in Uganda and was first introduced in northern Lake Victoria in 2010. An environment monitoring study was undertaken at Source of the Nile, a private cage fish farm, in Napoleon gulf, northern Lake Victoria. In-situ measurements of key environmental (temperature, dissolved oxygen, pH and conductivity) and biological (algae, zooplankton, macro-benthos) variables were made at three transects: Transect 1- the site with fish cages (WC); transect 2- upstream of the fish cages (USC-control) and Transect 3- downstream of the cages (DSC). Upstream and Downstream sites were located approximately 1.0 km from the fish cages. Environment parameters varied spatially and temporally but were generally within safe ranges for freshwater habitats. Higher concentrations of SRP (0.015-0.112 Mg/L) occurred at USC during February, September and at DSC in November; NO2-N (0.217- 0.042 mg/L) at USC and DSC in February and November; NH4-N (0.0054- 0.065 Mg/L) at WC and DSC in February, May and November. Algal bio-volumes were significantly higher at WC (F (2,780)=4.619; P=0.010). Zooplankton species numbers were consistently lower at WC with a significant difference compared to the control site (P=0.032). Macro-benthos abundance was consistently higher at the site with cages where mollusks and low-oxygen and pollution-tolerant chironomids were the dominant group. Higher algal biomass, concentration of low-oxygen/pollution-tolerant macro-benthos and depressed zooplankton diversity at WC suggested impacts from the fish cages on aquatic biota.

Technical report on the environmental monitoring of the cage area at the Source of the Nile (SON) Cage Fish Farm for quarter 4: October-December 2015

Source of the Nile (SON) Cage Fish farm is located at Bugungu in Napoleon Gulf, northern Lake Victoria, near the headwaters of the River Nile. NaFIRRI has, through a Public-Private collaborative partnership with SON management, undertaken quarterly monitoring of the cage fish farm since 2011. The objective of the environment monitoring is to track possible environment and biological changes as a result of fish cage operations in the area. The agreed study areas cover selected physical-chemical parameters i.e. water depth, transparency, column temperature, dissolved oxygen, pH and conductivity; nutrient status; and biological parameters i.e. algae, zooplankton, macro-benthos and fish communities. The fourth quarter survey, which is the subject of this report was undertaken during December 2015. Results/observations made are presented in this technical report along with a scientific interpretation and discussion of the results with reference to possible impacts of the cage facilities to the water environment and aquatic biota. The present report presents field observations made for the fourth quarter survey undertaken in December 2015 and provides a scientific interpretation and discussion of the results with reference to possible impacts of the cage facilities to the water environment and the different aquatic biota in and around the fish cage site.

Technical report on the environmental monitoring of the cage area at the Source of the Nile (SON) Fish Farm for quarter 2: April-June 2015

Source of the Nile Fish farm (SON) is located at Bugungu area in Napoleon Gulf, northern Lake Victoria. The proprietors of the farm have a collaborative arrangement with NaFIRRI to undertake quarterly environment monitoring of the cage site as is mandatory under the NEMA conditions. The monitoring surveys cover selected physical-chemical factors i.e. water column depth, water transparency, water column temperature, dissolved oxygen, pH and conductivity; nutrient status, algal and invertebrate communities (micro-invertebrates/zooplankton and macroinvertebrates/ macro-benthos) as well as fish community. The second quarter survey for the calendar year 2015, which is the subject of this report, was undertaken in June 2015. Results/observations made are presented in this technical report along with a scientific interpretation and discussion of the results with reference to possible impacts of the cage facilities to the water environment and aquatic biota.

Invertebrate communities of Lake Nabisojjo

Invertebrates are organisms without a backbone on the basis of body size. Aquatic invertebrates can be divided into two broad categories: micro-and macro-invertebrates. The former commonly known as zooplankton, ranging in size from < 100um 10 ca.1500um and are mainly planktonic (i.e living suspended in the water column). The latter, also known as benthos, (bottom dwelling) are associated with bottom sediments(ie, living on sediment surface or burrowing in sediments), are much bigger organism greater than 1500um in body size.

Ecology of macrozoobenthic communities in two plateau lakes of Southwest China

Ecological studies on macrozoobenthos were conducted in two small plateau lakes in the Yunnan-Guizhou Plateau, Southwest China: Xingyun Lake (XL), a eutrophic lake whose main source of primary production was phytoplankton (Chl a=99.76 +/- 24.01 mu g/L), and Yangzong Lake (YL), a mesotrophic lake. Sampling was carried out from October 2002 to May 2004. Altogether 23 benthic taxa were identified in XL and 21 taxa in YL. The density of benthos in XL was much lower than that in YL, but the biomass was about equal in the two lakes, being 1 423 ind/m(2) and 8.71 g/m(2) in XL and 4 249 ind/m(2) and 8.60 g/m(2) in YL. The dominant species were Limnodrilus hoffmeisteri, Branchiura sowerbyi, Aulodrilus pluriseta and Chironomus sp. in XL and Limnodrilus hoffmeisteri, Aulodrilus pluriseta and Bellamya sp. in YL. Seasonal fluctuation occurred, showing richer species in summer and winter, but the density and biomass varied in different ways in the two lakes. Analyses on functional feeding groups indicate that collector-gatherers were predominant, but the relative abundances of other groups were different. Stepwise multiple regression analysis demonstrated that the water depth, conductivity and chlorophyll a were the key factors affecting macrozoobenthic abundance in the lakes.

Accumulation of hepatotoxic microcystins in freshwater mussels, aquatic insect larvae and oligochaetes in a large, shallow eutrophic lake (Lake Chaohu) of subtropical China

This paper studied the seasonal changes of two common microcystins (MCs), MC-RR and -LR, in the commercially important mussel Corbicula fluminea in Lake Chaohu, where there occurred dense cyanobacteria. Occasional measurements were also made for MC in the mussel Arconaia lanceolat, the oligochaete Limnodilus hoffineisteri and the insect larva Chironomus sp. Mean MC of C. fluminea was much higher in hepatopancreas than in intestine and foot. Our study is the first to report accumulation of MCs in oligochaetes and aquatic insect larvae. The hi-h contents of MCs in the insect larvae suggest a great possibility for the transfer of MCs to benthos-feeding omnivores like common carp. According to the provisional standard by the WHO, 28.6% of the collected C. fluminea were harmful for human consumption, assuming a daily consumption of 300 by a person. It is recommended that edible mussels should not be collected for human consumption during toxic cyanobacterial blooms in Lake Chaohu.

Macrozoobenthic community of Fuxian Lake, the deepest lake of southwest China

Located in the Yunnan-Guizhou Plateau in southwest China, Fuxian Lake covers an area of 211 km(2), with maximum depth of 155 m. It is known to have a unique fauna, including 14 described endemic species. In order to describe the zoobenthic community of the lake more completely, the present study was conducted from August 2002 to August 2003. Altogether 62 benthic taxa, including 22 oligochaetes, 21 molluscs and 18 insects were identified, of which the dominant taxa belonged to Potamothrix, Procladius and Paraprososthenia. The standing stocks of benthos were much higher in the littoral (824 ind/m(2) in density, 3.72 g/m(2) in biomass) than in the profundal region (23 ind/m(2) in density, 0.10 g/m(2) in biomass). Species richness was greatest in summer and standing stocks were larger in spring and summer than in other seasons. Analyses of functional feeding groups indicated that collector-gatherers and scrapers were predominant in entire lake. Stepwise multiple regression analysis demonstrated that the water depth is the most important factor affecting the distribution of macrozoobenthos. (C) 2008 Elsevier GmbH. All rights reserved.

Macrozoobenthic community of Poyang Lake, the largest freshwater lake of China, in the Yangtze floodplain

Poyang Lake (Poyang Hu) is located at the junction of the middle and lower reaches of the Yangtze (Changjiang) River, covering an area of 3283 km(2). As one of the few lakes that are still freely connected with the river, it plays an important role in the maintenance of the unique biota of the Yangtze floodplain ecosystem. To promote the conservation of Poyang Lake, an investigation of the macrobenthos in the lake itself and adjoining Yangtze mainstream was conducted in 1997-1999. Altogether 58 benthic taxa, including, 22 annelids, 8 mollusks, 26 arthropods, and 2 miscellaneous animals, were identified from quantitative samples. The benthic fauna shows a high diversity and a marine affinity. The standing crops of benthos in the lake were much higher than those in the river, being 659 individuals/m(2) and 187.3g/m(2) (wet mass) in the main lake, and 549 individuals/m(2) and 116.6 g/m(2) in the lake outlet, but only 129 individuals/m(2) and 0.4g/m(2) in the river. The dominant roup in the lake was Mollusca, comprising 63.4% of the total in density and 99.5% in biomass. An analysis of the functional feeding structure indicated that collector-filterers and scrapers were predominant in the lake, up to 42.2% and 24.7% in density and 70.2% and 29.2% in biomass, respectively, while shredders and collector-gatherers were relatively common in the river. The present study was restricted to the northern outlet and the northeast part of Poyang Lake. A scrutiny is required for the remaining areas.

MOBILITY AND TRANSFER OF RESIDUAL HEXACHLOROCYCLOHEXANE (HCH) IN AQUATIC ENVIRONMENT

An investigation was carried out to study the mobility and transfer of HCH-residues in Yanjia lake, Hubei, China, from 1990-1993. By sampling at different locations, the horizontal distribution of HCH-residues was determined; by sampling at different depths in the same location, the vertical mobility of HCH-residues and its penetration were measured. The vertical profiles of HCH-residues in sediment showed a gradient distribution, which was reduced with the increase in depth. This was very similar in shape to the organic carbon and nitrogen content profiles. The penetration of HCH-residues was measured as 60cm approximately. Meanwhile, water, sediment (0-12cm), benthos and benthic fish collected from the lake were analyzed to determine the transfer of HCH-residues along aquatic food chain. The BCF values of HCH-residues indicated that the bioaccumulation of HCH-residues in freshwater food chain still exsisted in spite of the banning of HCH since 1983. The maxium BCF value of HCH-residues in the liver samples of 5-year-old common carp was up to 61966 (calculated by beta-HCH).

九寨沟核心景区湖泊硅藻的组成及其密度与环境因子的关系

九寨沟自然保护区地处四川盆地北部岷山山脉南段，属川西高原气候中的暖温带。保护区内分布着118 个串珠状排列的高山湖泊，核心景区共有湖泊20 个（组），集中在海拔2000 米到3000 米之间。水资源是九寨沟的灵魂，保护水生生态系统是九寨沟生态旅游可持续发展的立足之本。本研究以九寨沟湿地生物多样性保护项目为依托，于2007 年5 月～2008 年4 月对九寨沟核心景区湖泊水体硅藻植物进行调查，分析了其密度与环境因子的相互关系，旨在为九寨沟湖泊生态系统保护提供科学依据和基础资料。主要有以下几点结论： （1）九寨沟硅藻植物丰富，调查统计为2 纲6 目10 科35 属159 种（包括变种和变型），水体硅藻中真性浮游种类较少，着生种类多，羽纹纲的脆杆藻属、舟形藻属、桥弯藻属、异极藻属、曲壳藻属的种类最多，常为优势属组成湖泊硅藻群落，只在长海是小环藻属占绝对优势。 （2）九寨沟水体中硅藻细胞密度不大，多在4×104～30×104 个/L，长海最高，五花海最低。在年变化上，不同的湖泊水体中硅藻的生长高峰季节不尽相同，在夏季、秋末和冬末春初均有可能出现高密度。在空间上，整体看来密度与海拔有一定的正相关，但由于水温不是单一主导因素，密度受多种环境因子影响，在海拔梯度上呈现一定的波浪状变化。 （3）影响九寨沟湖泊水体硅藻细胞密度较重要的环境因子是海拔、水温和pH。硅藻细胞密度年变化幅度大的湖泊水体，年平均细胞密度大。因此，环境因素不太稳定的湖泊水体，更可能出现高的硅藻细胞密度。11 月份响应于水量剧烈的减少，细齿菱形藻大量出现在五彩池成为优势种群，造成水体硅藻细胞密度的大幅增加。 （4）九寨沟湖泊水体水质几乎达到国家地表水I 类标准，但是，硅藻商指数以及代表多样性的Cairns 指数计算的结果不能反映水质的情况，这是由于水质状况不是决定九寨沟湖泊水体中硅藻生存的种类和数量的主要因素。因此在用各种指数分析水质的时候，都应该先判断计算该指数的参数是否主要由水质状况决定，然后再综合理化性质等其他指标分析和比较。 （5）人类的活动对九寨沟湖泊水生态系统有一定的影响。一方面，在低海拔景点人类活动的干扰比海拔高处相对要大，干扰引起低海拔景点湖泊硅藻Cairns指数较高；另一方面，旺季的影响比淡季大，水体中出现了典型富营养种类。因此，应加强低海拔景点和旺季的管理，并限制淡季的人类活动以保证九寨沟生态系统的自我恢复。 Jiuzhaigou nature reserve is located in north Sichuan, at the south section of Minshan Mountain, having a warm temperate climate which belongs to West Sichuan plateau climate. It includes 118 mountain lakes, and 20 of them between 2000 and 3000 altitude degree constitute the core area of Jiuzhaigou. The water is Jiuzhaigou's soul, so it is the basis of sustainable tourism development of Jiuzhaigou to protect the water ecological environment. Research depends on Jiuzhaigou wetland biodiversity protection program in this paper, invested the diatom plants in 17 lakes at the core area from May 2007 to April 2008. The composition and the correlation of diatom density and the environment were studied, which could provide scientific and basic information for the protection of the ecological environment of Jiuzhaigou. The main conclusions were: 1 The diatom species were in abundance, investigation showed that there were 159 species belong to 10 families and 35 genera. Most diatoms were benthos, euplankton were less. Genera Fragilaria, Navicula, Cymbella, Gomphonema and Achnanthes had the most species, which always were the dominant genera. Only in The Long Lake genus Cyclotella possessed a predominant status. 2 The diatom cell density was not very high, always between 4×104 cell/L and 30×104 cell/L, highest in The Long Lake and lowest in The Colorful Lake. In one year's time, diatom in different lakes had different growth type. The maximum could be in summer, late autumn and late winter early spring. The cell density showed a positive correlation to altitude in the whole, but fluctuated in details along altitude because of comprehensive influence by many environmental factors. 3 Altitude, water temperature and pH were the more important factors to determine the cell density. There was a positive correlation between the range of cell density in one year and the average cell density. So high annual cell average density probably will appear in lakes which has an unstable environmental condition. The boom of Denticula elegans in The Jade-Colored Lake in November was corresponding to the large decrease in water quantity. 4 The water quality of Jiuzhaigou was near the National Surface Water Standard rank I, but the Diatom Quotient and the Cairns Index didn't reflect the water quality accordingly. It was because the water quality wasn't the most important factor here which determined the species number and species quantity, so the index based on these items would not reflect it. Therefore, it is recommended that, when we use indices to evaluate the water quality, we should know first whether the water quality is the main determinative factor inflects the items used to compute the indices, and then combined with other chemical indices to analyze and do comparison. 5 The tourists' activities had influenced the water ecosystem of Jiuzhaigou. On the one hand, disturbance was relatively high at the lower altitude, it resulted in higher Cairns index; on the other hand, influence in high season was more severe than in low season, some typical species indicating eutrophication were observed in the water. It is suggested that the management at lower altitude and in high season must be strengthen, and less people activity in low season is necessary to fulfill the recovery of the water ecosystem.

Studies on the regional feature of organic carbon in sediments off the Huanghe River Estuary waters

Organic carbon (OC) in definitely small area sediments(according to marine dimension)off the Huanghe River Estuary is investigated in order to evaluate the feature of regional difference of physical and chemical properties in marginal sea sediments. The distributions of OC in sediments with natural grain size and the relationship with the pH, Eh,Es and Fe3+/Fe2+ are discussed. In addition,OC decomposition rates in surfacial/subsurfacial sediments are estimated. OC concentrations range from 0.26% to 1.8%(wt)in the study area. Significant differences in OC content and in horizontal distribution as well as various trends in surfacial/subsurfacial sediments exhibit the feature of regional difference remarkably in marginal sea sediments. The complicated distribution of OC in surface sediments is due to the influence of bacterial activity and abundance, bioturbation of benthos and physical disturbance. The OC decomposition rate constant in surfacial/subsurfacial sediments ranges from 0.0097 to 0.076 a(-1) and the relatively high values may be mainly related to bacteria that are mainly responsible for OC mineralization;meio-and macrofauna affect OC degradation both directly, through feeding on it, and indirectly through bioturbation and at the same time coarse sediments are also disadvantageous to OC preservation. In almost all the middle and bottom sediments the contents of OC decrease with the increase of deposition depth, which indicates that mineralization of OC in the middle and bottom sediments has occurred via processes like SO42- reduction and Fe-oxide reduction.

Density-dependent effects on seston dynamics and rates of filtering and biodeposition of the suspension-cultured scallop Chlamys farreri in a eutrophic bay (northern China): An experimental study in semi-in situ flow-through systems

Effects of stocking density on seston dynamics and filtering and biodeposition by the suspension-cultured Zhikong scallop Chlamys farreri Jones et Preston in a eutrophic bay (Sishili Bay, northern China), were determined in a 3-month semi-field experiment with continuous flow-through seawater from the bay. Results showed that the presence of the scallops could strongly decrease seston and chlorophyll a concentrations in the water column. Moreover, in a limited water column, increasing scallop density could cause seston depletion due to scallop's filtering and biodeposition process, and impair scallop growth. Both filtration rate and biodeposition rate of C. farreri showed significant negative correlation with their density and positive relationship with seston concentration. Calculation predicts that the daily removal of suspended matter from water column by the scallops in Sishili Bay ecosystem can be as high as 45% of the total suspended matter; and the daily production of biodeposits by the scallops in early summer in farming zone may amount to 7.78 g m(-2), with daily C, N and P biodeposition rates of 3.06 x 10(-1), 3.86 x 10(-2) and 9.80 x 10(-3) g m(-2), respectively. The filtering and biodeposition by suspension-cultured scallops could substantially enhance the deposition of total suspended particulate material, suppress accumulation of particulate organic matter in water column, and increase the flux of C, N and P to benthos, strongly enhancing pelagic-benthic coupling. It was suggested that the filtering-biodeposition process by intensively suspension-cultured bivalve filter-feeders could exert strong top-down control on phytoplankton biomass and other suspended particulate material in coastal ecosystems. This study also indicated that commercially suspension-cultured bivalves may simultaneously and potentially aid in mitigating eutrophication pressures on coastal ecosystems subject to anthropogenic N and P loadings, serving as a eutrophic-environment bioremediator. The ecological services (e.g. filtering capacity, top-down control, and benthic-pelagic coupling) functioned by extractive bivalve aquaculture should be emphasized in coastal ecosystems. (c) 2005 Elsevier B.V. All rights reserved.