Seasonal variation in primary productivity in three tropical ponds

Summary Primary productivity values ranged from 1.5 to 15.8 gc/M²/day in Othakadai pond; 2.0 to 8.0 gc/M²/day in Teppakulam tank and 1.05 to 5.4 gc/M²/day in Yanamalai pond. Among the three ponds, highest annual yield was recorded in Othakadai pond (2000.2 gc/M²/yr) next in order comes Teppakulam tank (1211.8 gc/M²/yr) and lastly Yanamalai pond (810.7 gc/M²/yr). In all three ponds temperature and chlorophyll-a showed a more or less direct correlation to productivity values. Alkalinity values and productivity values showed a positive correlation in Othakadai and Yanamalai ponds, while no relationship between alkalinity and productivity could be established in Teppakulam tank.Formed part of a Ph. D. Thesis submitted to Madurai University.     

盐碱池塘浮游植物初级生产力日变化的研究

用黑白瓶测氧法对盐碱池塘浮游植物初级生产力的日变化进行了研究．结果表明,盐碱池塘浮游植物初级生产力存在着明显的日变化,其分布规律与光照、温度、浮游植物现存量等环境因子的变化是相关的．用黑白瓶法连续曝光24h测定初级生产力结果大大偏低于每次曝光2h的全天累积结果．对养鱼池而言,在10：00—14：00时曝光4h再推算全天的初级生产力较为适当．     

Effect of light intensity on sulfate uptake and primary productivity by natural freshwater microplankton communities and axenic algal cultures

Analyses of four years of in situ sulfate uptake by microplankton communities in two,trophically different lakes showed that about 12% of the experiments had dark uptake equal to or higher than uptake at ambient light. Three axenic algal cultures subjected to different light intensities showed that sulfate uptake patterns, relative to primary productivity, vary with species and although sulfate uptake tends to decrease at lower light levels, at or very near darkness, in physiologically active (young) cultures sulfate uptake frequently increases dramatically. The field data, when summarized according to the light received, shows the same trends seen in the axenic cultures. It is concluded that sulfate uptake is only loosely associated with inorganic carbon uptake (primary productivity) and that under some circumstances a low level of light may increase the sulfate uptake rate.     

Impact of exotic fish removal on native communities in farm ponds

Introduced largemouth bass (Micropterus salmoides spp.) and bluegill (Lepomis macrochirus spp.) are thought to threaten native aquatic organisms worldwide and hence their eradication has recently begun in Japan. Our previous studies suggested that the removal of largemouth bass increases native fish, shrimp, dragonflies, and exotic crayfish, but decreases macrophytes. To test this prediction, we removed the exotic fishes by draining farm ponds and compared the numbers of these organisms before and after the drain, as well as between drained and undrained ponds. The number of dragonfly Pseudothemis zonata, crayfish, shrimp, and goby increased rapidly after the drain, but the coverage of macrophyte declined. The reduction in macrophyte is assumed to be caused by increased herbivory by crayfish. The number of exuviae of damselfly Cercion calamorum and the total number of species of odonate also decreased after the drain. These decreases can be due to the reduction of macrophyte because reduced odonate species are known to use macrophytes as oviposition sites. Therefore, the removal of largemouth bass has a potential to cause negative effects on some native organisms. We propose that reduction of exotic crayfish should be considered when eradicating the exotic fishes.     

The response of amphibian communities to fish and habitat features in Mediterranean permanent ponds

Generalized linear models were used to test the effect of fish, using ponds with and without fish and habitat features as covariates, on richness and abundance of amphibian species. Five fish species and six amphibian species were recorded in 60 permanent ponds located in central Italy. The choice of covariates (macrophyte cover and pond surface area) was made after studying the correlations. The richness of amphibian species was not significantly affected by fish presence or macrophyte cover, in line with previous studies, since almost all the fish species were non-predatory. However, abundance of urodeles (newts) was negatively affected by fish and positively affected by macrophyte cover. Although fish may strongly influence the abundance and composition of amphibian communities, the results indicate that the cover of aquatic macrophytes may increase the available habitat for amphibians and therefore their abundance. Anuran species preferred ponds where fish were present, since both groups preferred larger ponds. Concordance between fish and amphibian species composition was not found by the Mantel and Partial Mantel tests. This indicates that the fish assemblages do not predict which amphibian species occur in the pond.     

Modelling photosynthesis in shallow algal production ponds

Shallow ponds with rapidly photosynthesising cyanobacteria or eukaryotic algae are used for growing biotechnology feedstock and have been proposed for biofuel production but a credible model to predict the productivity of a column of phytoplankton in such ponds is lacking. Oxygen electrodes and Pulse Amplitude Modulation (PAM) fluorometer technology were used to measure gross photosynthesis (P _G) vs. irradiance (E) curves (P _G vs. E curves) in Chlorella (chlorophyta), Dunaliella salina (chlorophyta) and Phaeodactylum (bacillariophyta). P _G vs. E curves were fitted to the waiting-in-line function [P _G = (P _Gmax × E/E_opt) × exp(1 — E/E_opt)]. Attenuation of incident light with depth could then be used to model P _G vs. E curves to describe P _G vs. depth in pond cultures of uniformly distributed planktonic algae. Respiratory data (by O2-electrode) allowed net photosynthesis (P _N) of algal ponds to be modelled with depth. Photoinhibition of photosynthesis at the pond surface reduced P _N of the water column. Calculated optimum depths for the algal ponds were: Phaeodactylum, 63 mm; Dunaliella, 71 mm and Chlorella, 87 mm. Irradiance at this depth is ≈ 5 to 10 μmol m^?2 s^?1 photosynthetic photon flux density (PPFD). This knowledge can then be used to optimise the pond depth. The total net P _N [μmol(O2) m^?2 s^?1] were: Chlorella, ≈ 12.6 ± 0.76; Dunaliella, ≈ 6.5 ± 0.41; Phaeodactylum ≈ 6.1 ± 0.35. Snell’s and Fresnel’s laws were used to correct irradiance for reflection and refraction and thus estimate the time course of P _N over the course of a day taking into account respiration during the day and at night. The optimum P _N of a pond adjusted to be of optimal depth (0.1–0.5 m) should be approximately constant because increasing the cell density will proportionally reduce the optimum depth of the pond and vice versa. Net photosynthesis for an optimised pond located at the tropic of Cancer would be [in t(C) ha^?1 y^?1]: Chlorella, ≈ 14.1 ± 0.66; Dunaliella, ≈ 5.48 ± 0.39; Phaeodactylum, ≈ 6.58 ± 0.42 but such calculations do not take weather, such as cloud cover, and temperature, into account.     

Coral–algal phase shifts alter fish communities and reduce fisheries production

Anthropogenic stress has been shown to reduce coral coverage in ecosystems all over the world. A phase shift towards an algae‐dominated system may accompany coral loss. In this case, the composition of the reef‐associated fish assemblage will change and human communities relying on reef fisheries for income and food security may be negatively impacted. We present a case study based on the Raja Ampat Archipelago in Eastern Indonesia. Using a dynamic food web model, we simulate the loss of coral reefs with accompanied transition towards an algae‐dominated state and quantify the likely change in fish populations and fisheries productivity. One set of simulations represents extreme scenarios, including 100% loss of coral. In this experiment, ecosystem changes are driven by coral loss itself and a degree of habitat dependency by reef fish is assumed. An alternative simulation is presented without assumed habitat dependency, where changes to the ecosystem are driven by historical observations of reef fish communities when coral is lost. The coral–algal phase shift results in reduced biodiversity and ecosystem maturity. Relative increases in the biomass of small‐bodied fish species mean higher productivity on reefs overall, but much reduced landings of traditionally targeted species.     

Design features of constructed floodplain ponds influence waterbird and fish communities in northern New Zealand

1. Ponds can provide important refuges for aquatic biota on developed floodplains and are increasingly being constructed in an effort to enhance native biodiversity and ecosystem services in degraded landscapes. This study examined 34 constructed ponds to investigate the influence of design features on community composition, native biodiversity, and the biomass or abundance of common fish and waterbirds on the lower Waikato River floodplain, northern New Zealand.
2. Inundation frequency appeared to be a key factor affecting biomass of the native shortfin eel Anguilla australis and three invasive fish species (common carp [Cyprinus carpio], brown bullhead [Ameiurus nebulosus], and goldfish [Carassius auratus]), suggesting that colonisation occurred during flooding by adjacent waterbodies. Linear models indicated that shortfin eel abundance and total eel biomass were positively associated with the biomass of potential fish prey, the area occupied by islands and cover by trees in the riparian zone.
3. Native waterbird species richness was strongly related to water area, edge length (including islands) and area:perimeter ratio, with little increase in richness for ponds >1 ha in area, perimeters longer than 800 m, and ratios over 20. The protected grey teal (Anas gracilis), and the recreationally hunted species phenotypically assigned as mallard (Anas platyrhynchos + hybrids) and grey duck (Anas superciliosa + hybrids) appeared most strongly influenced, respectively, by perimeter length, water depth, and biomass of potential macroinvertebrate food supplies, suggesting variable effects of pond design attributes among waterfowl species.
4. Overall, these results indicate that constructed ponds can be designed to promote native waterbird diversity, enhance eel fishery and waterfowl gamebird services, and also limit the proliferation of some non-native invasive fish species in degraded floodplain landscapes. A hierarchy of constructed pond design attributes was identified, involving landscape position and connectivity, pond morphology and complexity, and riparian maturity and buffering, which were associated with direct (habitat) and indirect (food supply, physicochemistry) effects on biodiversity and provisioning services.

     

Fertilization effects on species density and primary productivity in herbaceous plant communities

Fertilization experiments in plant communities are often interpreted in the context of a hump-shaped relationship between species richness and productivity. We analyze results of fertilization experiments from seven terrestrial plant communities representing a productivity gradient (arctic and alpine tundra, two old-field habitats, desert, short- and tall-grass prairie) to determine if the response of species richness to experimentally increased productivity is consistent with the hump-shaped curve. In this analysis, we compared ratios of the mean response in nitrogen-fertilized plots to the mean in control plots for aboveground net primary productivity (ANPP) and species density ( D ; number of species per plot of fixed unit area). In general, ANPP increased and plant species density decreased following nitrogen addition, although considerable variation characterized the magnitude of response. We also analyzed a subset of the data limited to the longest running studies at each site (≥4 yr), and found that adding 9 to 13 g N m⁻² yr⁻¹ (the consistent amount used at all sites) increased ANPP in all communities by approximately 50% over control levels and reduced species density by approximately 30%. The magnitude of response of ANPP and species density to fertilization was independent of initial community productivity. There was as much variation in the magnitude of response among communities within sites as among sites, suggesting community-specific mechanisms of response. Based on these results, we argue that even long-term fertilization experiments are not good predictors of the relationship between species richness and productivity because they are relatively small-scale perturbations whereas the pattern of species richness over natural productivity gradients is influenced by long-term ecological and evolutionary processes.     

Phytoplankton communities in channel catfish ponds

Seasonal changes in the quantity and quality of phytoplankton were studied in six channel catfish culture ponds. Chlorophyll a concentrations were generally highest in the summer (averaging >200 g 1^–1) but the highest individual chlorophyll a value recorded (910 g 1^–1) occurred in the winter during a bloom of Dictyosphaerium pulchellum. On the average, green algae (Chlorophyta) and euglenoids (Euglenophyta) represented relatively constant proportions of the phytoplankton community seasonally (about 35 and 10%, respectively). In the summer and fall, blue-green algae (Cyanophyta) became abundant. Diatoms were relatively abundant at all times and constituted the majority of the community in the winter and spring.     

Characteristics of plankton communities in Chinese integrated fish ponds: effects of excessive grazing by planktivorous carps on plankton communities

Biomass and production of plankton communities were investigated in two Chinese integrated fish culture ponds in August, Dianshanhu Pond (with high density of planktivorous carp) and Pingwang Pond (with low density of planktivorous carp). The plankton communities were composed of rotifers, protozoans, phytoplankton (<40 µm) and bacteria. The large phytoplankton (>40 µm), cladocerans and copepods were rare because of grazing pressure by the carp. The density or biomass of bacteria (1.93 × 10⁷ and 2.20 × 10⁷ cells ml^–1 on average in Dianshanhu and Pingwang Ponds, respectively), picophytoplankton (24.6 and 18.5 mg m^–3 Chla on average) and rotifers (5372 and 20733 ind. 1^–1 on average) exceeded the maximum values reported for natural waters.The average [³H]thymidine uptake rates were 694 and 904 pmoles 1^–1 h^–1 (13.4 and 20.6 µgC 1^–1) and the bacterial production by the >2 µm fraction amounted 21–28% of total [³H] thymidine uptake rate in both ponds. The mean chlorophylla concentrations were 59.1 and 183 mg m^–3 in Dianshanhu and Pingwang Ponds, respectively. 82.4% and 65.3% of the total Chla was contributed by the <10 µm nano- and picophytoplankton in each pond, respectively. In particular, the picophytoplankton contribution amounted 41.2% of thtal Chla in Dianshanhu Pond. Primary production was 2.5 and 3.4 gC m^–2 d^–1 in each pond, respectively, and >50% of production was contributed by picophytoplankton. The mean biomasses of protozoa were 168 µg 1^–1 and 445 µg 1^–1 and those of rotifers were 763 µg 1^–1 and 1186 µg 1^–1 in Dianshanhu and Pingwang Ponds, respectively. The ecological efficiencies expressed in terms of the ratios of primary production to zooplankton production were 0.22 and 0.31, for the two ponds.     

Epilithic algal communities in hypogean environments

Abstract

The dominant algae colonizing hypogean sites are usually epilithic cyanophytes which are often associated with chlorophytes and diatoms, and sometimes mosses. High relative humidity and extremely low photon fluxes characterize the environment in which a prevalence of shade-adapted species is supposed. The interactions with the substrate and the light adaptation of the algae encountered is discussed also in relation to biodeterioration processes. The taxa occurring in hypogea are reported in comparison with cave vegetation. The phototrophic communities support the growth of abundant bacterial populations.     

Summer zooplankton communities of selected borrow-pit ponds in Northern Illinois,U.S.A.

Zooplankton samples were collected from 7 borrow-pit ponds during the summer months of 1975 in northern Illinois. Species diversity indices and evenness values were used to characterize the ponds zooplankton community structure. Thirty-one plankton species are reported. Older borrow-pit ponds contained more species and had higher mean densities than did the newer ponds. The number of dominant species reported per pond varied from 1 to 4. Species diversity indices are higher in older ponds, and there was a general tendency for species diversity to increase with pond age. No correlations between physicochemical measurements and the structure of the zooplankton communities were found. Factors possibly governing zooplankton community structure in borrow-pits are speculated upon.     

Effects of algal canopy clearance on plant, fish and macroinvertebrate communities on eastern Tasmanian reefs

Changes in assemblages of plants, macroinvertebrates and fishes on three eastern Tasmanian reefs were monitored over 12 months in replicated control blocks and adjacent 10×12-m blocks cleared of fucoid, laminarian and dictyotalean algae. Removal of canopy-forming plants produced less change to biotic assemblages than reported in studies elsewhere, with the magnitude of change for fish and invertebrate taxa lower than variation between sites and comparable to variation between months.The introduced annual kelp Undaria pinnatifida exhibited the only pronounced response to canopy removal amongst algal taxa, with a fivefold increase in cleared blocks compared to control blocks. Marine reserves are suggested to assist reef communities resist invasion by U. pinnatifida, through an indirect mechanism involving increased predation pressure on sea urchins and reduced formation of urchin barrens that are amenable to U. pinnatifida propagation.Large invertebrates were more associated with turfing algae or the reef substratum than the macroalgal canopy. The herbivorous sea urchin Heliocidaris erythrogramma and abalone Haliotis ruber showed the strongest response to clearing amongst common macroinvertebrate species, with a halving of population numbers. Observed densities of the common monacanthid fish Acanthaluteres vittiger also declined by about 50%. The relatively high level of resistance shown by eastern Tasmanian reef biota to patch disturbance was attributed largely to high diversity and biomass of turfing macroalgae damping effects of canopy clearance.     

Summer fish communities in northern Gulf of Mexico estuaries: Indices of ecological condition

We used fish community data from trawl samples collected from >100 estuaries, bayous, and coastal lagoons of the Louisianan Biogeographic Province (Gulf of Mexico) to develop indicators of large-scale ecological condition. One data set, from which we derived reference values for fish community indicators, was based on bottom trawl samples collected from 367 randomly located sites during the summers of 1992–1994. A second trawl data set with similar geographic scope from 2000 to 2004 was used to test the robustness of the indicators derived from the reference data set to new data. We constructed a fish community index (FCI) from three basic indicators: number of species per trawl, total abundance per trawl, and an index of trophic balance among three common feeding guilds. The FCI was not correlated with salinity over a range from freshwater to marine and hypersaline conditions (0–52 psu). Direct correlations between the index and environmental variables generally were weak, although some were significant (p < 0.05). The FCI was negatively correlated with water clarity (secchi depth), water column depth, and sediment toxicity; correlations of the FCI with pH, sediment organic carbon, and sediment silt + clay content were positive. There was a hyperbolic relationship between dissolved oxygen and maximum values of the index, and no significant correlation with watershed land cover at the whole-estuary or estuary-complex scale. Values of all indicators increased between the two time periods. The FCI is a broad indicator of ecological condition for estuaries within the Louisianan Province, with data aggregated at scales ranging from large estuaries to the entire region. Sample density was insufficient to judge performance of the indicators or index at smaller scales.     

高寒草地植物群落地上-地下净初级生产力权衡

植物生产力分配和权衡是植物生态学研究中的热点,反映植物对环境的适应性,是了解植物响应全球气候变化的关键。青藏高原作为气候变化敏感区,研究其植物地上与地下部分权衡对了解高寒草地植被生存策略和生态系统可持续发展具有重要意义。目前,生物量分配调控机制已被广泛研究,但主要使用植物根冠比和地上-地下生物量比等方法来表征植物分配模式,缺乏考虑因植物生长周期导致的差异。使用青藏高原高寒草地103个样点的地上和地下净初级生产力数据,分析高寒草甸和高寒草原两种主要草地类型的地上-地下净初级生产力权衡关系。利用气候因素和土壤因素等相关数据,结合方差分析、相关分析、相对重要性分析和结构方程模型的方法,探究环境因素对两种草地类型地上-地下净初级生产力权衡的影响机制。研究发现：（1）高寒草甸的地上净初级生产力、地下净初级生产力和土壤养分含量显著高于高寒草原（P<0.05）;（2）高寒草地植被生产力均向地下权衡（0.0199）,且高寒草原（0.0354）的权衡值高于高寒草甸（0.0173）;（3）结构方程模型发现,年平均降水量、土壤容重和土壤速效氮含量是影响高寒草甸生产力权衡的主导因子,而年平均温度和年平均降水量是影响高寒草原生产力权衡的主导因子。研究表明高寒草甸的生产力权衡主要受气候和土壤因素共同影响,而高寒草原主要受气候因素调节。研究为理解植物地上-地下生物量分配调控机制提供了新的视角和方法,对系统了解高寒草地生物量分配模式和准确预测高寒草地植被动态过程具有指导意义。     

Competitive relationships in natural and artificial algal communities

Modern data on competitive relationships and their role in the succession of natural and artificial algal communities are reviewed. The mechanisms of macroalgae competition and the factors that affect the competitive outcomes are considered. The conception of competitive interactions between seaweeds in the field and culture is suggested. (1) Competitive relationships are possible only between seaweeds which live together and are able to exchange signals. (2) Success in the competition for light is the basis for wins in the competition for space. (3) The competition for nutrients never results directly in the exclusion of the competitor from the community. It inhibits the competitor and allows the winner to overgrow, shade, act allelopathically, and to displace the inferior competitor in the community. (4) People, creating an artificial monodominant community, either increase the competitive potential of cultivated species by selection of growth conditions or exclude the competitors.     

Net primary productivity and nitrogen and carbon distribution in two xerophytic communities of central-west Argentina

Net primary productivity and the nitrogen, carbon, and energy contents of the leaf, aerial wood and root components of the five most important woody dominants in two xerophytic forests in central-west Argentina were measured. Nitrogen and carbon contents of litter and mineral soil beneath individual plant canopies were also studied. The woody dominants in the 8-yr old ‘chaco’ woodland in Chamical, La Rioja, covered a greater proportion of total community area but had less aerial biomass than the 5 woody dominants of the 50-yr-old openProsopis flexuosa woodland in Ñacuñán, Mendoza. Marked differences in net primary production among species of the two communities were also noted (29–115 kg aerial biomass ha^?1 yr^?1 in the Chamicalvs 51–524 kg ha^?1 yr^?1 in the Ñacuñán woodland). Nitrogen in vegetation varied by species, and within species, varied by season and plant component. In general, leaf-N was higher in legumes in summer than in non-legumes in summer, and for most species higher in summer than in winter. Differences in %N in other plant components and in per cent C among species and seasons were less consistent. In both communities, soil N and C were higher and more variable with depth under individual plant canopies than in non-vegetated areas, and differences among species were apparent.     

The effects of an abandoned roast yard on the fish and macroinvertebrate communities of surrounding beaver ponds

Recently formed beaver-ponds surrounding an abandoned copper-nickel ore roast yard near Sudbury, Ontario, Canada, were influenced by highly acidic and heavy-metal contaminated effluent. Fish, including Culaea inconstans, Phoxinus neogaeus, Phoxinus eos, and Pimephales promelas, were found in the ponds upstream of the roast yard only. Macroinvertebrate taxon richness and diversity were greater in the upstream ponds than in the downstream ponds. Acid intolerant taxa, including Mollusca and Hyalella azteca, were found upstream only; acid tolerant taxa, including Enallagma and Ischnura (Odonata: Coenagrionidae) were found in the downstream ponds. One taxon, a species of Chironomus, was especially tolerant of both acid and metal stresses, and was the only invertebrate taxon found in the pond located directly on the roast yard itself. We conclude that long-abandoned mining and refining sites can continue to have a marked effect on aquatic communities.     

Nematode communities of small farmland ponds

The nematofauna of 14 farmland ponds, selected according to a gradient of surrounding agricultural land-use intensity, from five regions in North-West of Belgium were studied. The total nematode density (9–411 ind./10 cm2 per pond), and especially the number of species (4–12 species per pond) was especially low in these ponds. In total, 17 genera of free-living benthic nematodes, belonging to 15 families, are identified. Tobrilus gracilis and Eumonhystera filiformis were the most common species and were found in 13 and 12 of the 14 sampled ponds, respectively. The genera Tobrilus and Eumonhystera jointly comprise 77% of the total nematofauna. Consequently, the investigated water bodies were dominated by deposit feeding Monhysteridae and/or by chewing Tobrilidae. Diplogasteridae and Rhabditidae, normally related with eutrophic habitats, were almost absent. In order to explain the variation of total density, diversity, feeding-types composition and the individual density of the six most important species within ponds as well, sets of environmental variables were statistically selected. It was demonstrated that morphologically very similar species can show highly different ecological properties. The presence of a substantial mud layer and of an overall high level of eutrophication as well as the presence of possibly associated anaerobic conditions are put forward as the main factors explaining the observed low density and diversity. Total phosphate concentration and sediment characteristics seem to be the most important variables to explain the nematode community structure. However, a clear pattern of environmental variables, agricultural land use and nematode assemblages was not observed. Handling editor: K. Martens