Biomass Of Most Species Research Articles

Species-level associations of phytoplankton with environmental variability in the Neva Estuary (Baltic Sea)

Changes in phytoplankton communities due to anthropogenic nutrient load and climate change often lead to eutrophication and harmful algal blooms that can affect biogeochemical cycling. However, little is known about the specific responses of various species to environmental variables. 17-year long data on the midsummer phytoplankton biomass in the Neva Estuary were analyzed to show the changes in the composition of phytoplankton in relation to water depth, transparence, salinity, temperature, concentrations of total phosphorus and chlorophyll a, and plankton primary production. One hundred seventy-four species and forms from eight taxonomic classes were found in phytoplankton. Fifteen species were potentially harmful. The most diverse and abundant groups were cyanobacteria, green algae and diatoms. Canonical Correspondence Analysis showed that the biomass of various species from each phytoplankton group correlated differently with environmental factors. However, within each group, there were some predominant trends in the correlative response to changes in environmental variables. The biomass of cyanobacteria was high in the middle and lower reaches of the estuary and, in general, positively correlated with water salinity. The biomass of most species of green algae and diatoms correlated negatively with it. These algae showed a positive trend in biomass in the upper and middle reaches of the estuary during the last decades that may be explained by changes in weather conditions. Taking into account that climate models predict future increases in precipitation and temperature in the northern Baltic, the future expansion of freshwater phytoplankton species in estuaries of the northern Baltic Sea is very likely.

Ecological equivalence of species within phytoplankton functional groups

Summary There are tens of thousands of species of phytoplankton found throughout the tree of life. Despite this diversity, phytoplankton are often aggregated into a few functional groups according to metabolic traits or biogeochemical role. We investigate the extent to which phytoplankton species dynamics are neutral within functional groups. Seasonal dynamics in many regions of the ocean are known to affect phytoplankton at the functional group level leading to largely predictable patterns of seasonal succession. It is much more difficult to make general statements about the dynamics of individual species. We use a 7‐year time series at station L4 in the Western English Channel with 57 diatom and 17 dinoflagellate species enumerated weekly to test whether the abundance of diatom and dinoflagellate species varies randomly within their functional group envelope or whether each species is driven uniquely by external factors. We show that the total biomass of the diatom and dinoflagellate functional groups is well predicted by irradiance and temperature and quantify trait values governing the growth rate of both functional groups. The biomass dynamics of the functional groups are not neutral and each has their own distinct responses to environmental forcing. Compared to dinoflagellates, diatoms have faster growth rates and grow faster under lower irradiance, cooler temperatures, and higher nutrient conditions. The biomass of most species varies randomly within their functional group biomass envelope, most of the time. As a consequence, modellers will find it difficult to predict the biomass of most individual species. Our analysis supports the approach of using a single set of traits for a functional group and suggests that it should be possible to determine these traits from natural communities.

Arbuscular mycorrhizas in phosphate-polluted soil: interrelations between root colonization and nitrogen

To investigate whether arbuscular mycorrhizal fungi (AMF) – abundant in a phosphate-polluted but nitrogen-poor field site – improve plant N nutrition, we carried out a two-factorial experiment, including N fertilization and fungicide treatment. Percentage of root length colonized (% RLC) by AMF and tissue element concentrations were determined for four resident plant species. Furthermore, soil nutrient levels and N effects on aboveground biomass of individual species were measured. Nitrogen fertilization lowered % RLC by AMF of Artemisia vulgaris L., Picris hieracioides L. and Poa compressa L., but not of Bromus japonicus Thunb. This – together with positive N addition effects on N status, N:P-ratio and aboveground biomass of most species – suggested that plants are mycorrhizal because of N deficiency. Fungicide treatment, which reduced % RLC in all species, resulted in lower N concentrations in A. vulgaris and P. hieracioides, a higher N concentration in P. compressa, and did not consistently affect N status of B. japonicus. Evidently, AMF had an influence on the N nutrition of plants in this P-rich soil; however – potentially due to differences in their mycorrhizal responsiveness – not all species seemed to benefit from a mycorrhiza-mediated N uptake and accordingly, N distribution.

A Comparative Study of the Individual Biomass and Modular Biomass of 70 Herbaceous Species Found in the Horqin Sandy Land

In this study,the individual biomass and modular biomass of 70 herbaceous species in the Horqin Sandy Land were compared.The results showed that the individual biomass of 43 of the 70 species was less than 5.0 g,that the modular(root,stem,leaf and flower) biomass of most of the species was less than 2.0 g,and that the root-shoot ratios of 62 species was less than 1.These results indicate that the individual biomass of most species comes from aboveground biomass,and that just a few species have more branching roots and lateral roots.There is also a significant positive correlation between modular biomasses and the ratios of the modular biomass/individual biomass occur in an order of stem leaf root flower.There was no significant difference in the individual and modular biomass between annual or biennial species and perennial species.The ratios of stem biomass/individual biomass and aboveground biomass/individual biomass of annual or biennial species were significantly higher than those of perennial species,but the ratio of root biomass/individual biomass of perennial species was significantly higher than that of annual or biennial species.These characteristics are advantageous for the population diffusion and growth of different life-forms.The results also revealed that the arid climate and lean soil in the Horqin Sandy Land restrict the growth of plants,so the energy of most herbaceous species is utilized for growing their stems and leaves.

English

There is increasing interest among eastern U. S. landowners and coal operators in restoring mined land to native hardwood forests. Establishing a mix of native hardwood tree species simultaneously with erosion control ground covers is difficult. The purpose of this study was to test the response of hardwood species to three levels of ground cover control using an herbicide. Treatments were control (90% ground cover), spot spray around trees (50% cover), and broadcast spray (10% cover). Survival of oak species was generally greater when spot sprayed, but survival of ash, maple, poplar and white pine was unaffected. Tree biomass of most species was greater on spot sprayed plots. Trees on broadcast sprayed plots were damaged by herbicide drift rendering this treatment less effective. Overall stocking on spot sprayed plots was 67%, which met the stocking performance standard when 700 trees/acre were planted. A Forestland Reclamation Approach, which includes ground cover management, is needed for successful native hardwood reforestation.

Changes in the northern Benguela ecosystem over three decades: 1970s, 1980s, and 1990s

The northern Benguela ecosystem has been overfished and physically challenged over the past three decades. Ecopath with Ecosim was used to construct three ecosystem models (1971–1977, 1980–1989, and 1990–1995) and to compare differences in ecosystem structure. In the 1970s, the system sustained high catches, and had large populations of a few planktivorous fish. In the 1980s, the planktivorous fish species were expanded (horse mackerel, mesopelagic fish, and other small pelagics), although anchovy and sardine biomass was reduced. Catches remained high in the 1980s and the system was well connected. In the 1990s, the system was severely stressed, catches were much lower and omnivory was reduced. Most of the energy flowed through few pathways in the 1990s, and the energy was not transferred as efficiently up the trophic chain as in the 1980s. The fishery operated at the highest trophic level during the 1980s and there are some indications of “fishing down the foodweb” in this ecosystem between the 1980s and the 1990s. The high catches of sardine and hake in the 1970s are reflected in the high primary production required (PPR) by those compartments; the high catches of horse mackerel in the 1980s are shown by the high PPR for horse mackerel. The overall PPR for the fishery was highest in the 1980s, when the system was fished at nearly the same intensity as the 1970s, but the species taken were from higher trophic levels, requiring larger concentrations of primary production for their own existence. The importance of ecosystem–environmental interactions are highlighted by the abundance of horse mackerel, mesopelagics, small pelagics, and hake in the 1980s and the reduced biomass of most species in the 1990s, not only due to overfishing, but also due to the Benguela Niño that occurred in 1995. The system changed from an efficient ecosystem dominated by only two planktivores (anchovy and sardine) in the 1970s, to a system of large resilience and a varied planktivore population during the 1980s. However, the system’s resilience was lower, but its connectance was higher in the 1990s, where sardine was making a comeback and the marine mammals were doing well until the Benguela Niño reduced the system to a state of lower maturity.

Marsh terracing as a wetland restoration tool for creating fishery habitat

Terracing is a relatively new wetland-restoration technique used to convert shallow subtidal bottom to marsh. This method uses existing bottom sediments to form terraces or ridges at marsh elevation. A terrace field is constructed by arranging these ridges in some pattern that maximizes intertidal edge and minimizes fetch between ridges; the intertidal area is planted with marsh vegetation. We examined the habitat value of terracing for fishery species at Sabine National Wildlife Refuge, Louisiana (USA) in spring and fall 1999 by quantifying and comparing nekton densities in a 9-yr-old terrace field and nearby reference area using a 1-m2 drop sampler. Decapod crustaceans were more abundant than fishes, composing 62% and 95% of all organisms we collected in spring and fall, respectively. White shrimp Litopenaeus setiferus, daggerblade grass shrimp Palaemonetes pugio, blue crab Callinectes sapidus, and brown shrimp Farfantepenaeus aztecus accounted for 94% of all crustaceans, whereas 60% of all fishes were gulf menhaden Brevoortia patronus. Mean densities of white shrimp (fall), daggerblade grass shrimp, blue crab, and brown shrimp (spring) were significantly greater in terrace marsh than on non-vegetated bottom in the reference pond. Densities of most nekton on non-vegetated bottom were similar in the terrace field and the reference pond, but gulf menhaden and white shrimp had higher densities at terrace pond sites and brown shrimp (spring) were more abundant at reference pond sites. The pattern for biomass was similar to that for density in that the mean biomass of most species was significantly greater at terrace marsh sites than reference pond sites and similar at terrace and reference pond sites. Terrace marsh, however, was not functionally equivalent to natural marsh, as mean densities of daggerblade grass shrimp (fall), brown shrimp (spring), and blue crab and mean biomass of white shrimp (fall), striped mullet Mugil cephalus (spring), and spotted seatrout Cynoscion nebulosus (fall) were greater at reference marsh sites than terrace marsh sites. Using these density and biomass patterns and the percentage of marsh and pond area in the terrace field, we concluded that terrace fields support higher standing crops of most fishery species compared with shallow marsh ponds of similar size. Future restoration projects could include design changes to increase the proportion of marsh in a terrace field and enhance the habitat value of marsh terraces for fishery species.

Fish Communities of the Lower Fraser River (Canada) and a 21-year Contrast

Fish communities were sampled at 14 sites along the lower 120 km of the Fraser River, British Columbia by beach seine four times in 1972–1973 and three times in 1993–1994. Of the 37 species collected, peamouth chub, largescale sucker, starry flounder, and northern squawfish were predominant in either density or biomass. Densities and biomass of most species and all fish combined were higher in 1993–1994. Strong rank correlations of species abundance or biomass indicated that the overall fish community structure was very similar in both periods. At smaller spatial scales (reaches of 2–3 sites) and shorter time scales (by season), less than half the comparisons showed any significant correlation indicating changes in community composition. Largescale sucker, one of the largest contributors to biomass in both periods, showed decreased abundance, i.e., lower density, lower biomass, and large differences in the size-frequency distribution, specifically very low representation of small size classes. Other species, especially small-bodied forms, generally increased in numbers. Despite large changes in the lower Fraser River ecosystem in the past 21 years, the overall fish community has shown remarkably little change over that interval.

Effects of Ca (OH)2 additions on phytoplankton communities under ice cover in eutrophic hardwater lakes

The effects of Ca(OH) 2 treatment during the open-water season on phytoplankton communities under ice cover were examined for up to three winters (Nov. Apr.) in three eutrophic hardwater lakes in central Alberta. Phytoplankton communities were compared between treated and untreated lakes, and between pre- and posttreatment periods within a treatment lake. In all study lakes, phytoplankton biomass tended to be high at ice-on, decrease after November, and remain low (<2mg/L) from January to early March, when light conditions and water temperatures were also low. After late March to early April, phytoplankton biomass started to increase exponentially because of higher light conditions and water temperature. Most phytoplankton species that were common under ice also occurred during the open-water season. Although phytoplankton species composition was diverse under ice, the biomass of most species, except for flagellates, did not increase before mid-March. Species composition and biomass of some phytoplankton groups varied without clear trends among winters in treated and untreated lakes. Therefore, Ca(OH) 2 treatment during the open-water season did not appear to affect winter phytoplankton communities.

The Effects of Environmental Factors on Components and Attributes of a Meditteranean Grassland

1. The associations of six environmental factors with vegetative attributes on a species-rich Syrian grassland were investigated during 2 years with contrasting climatic conditions using an unreplicated factorial experiment. The six factors were (i) phosphate supply (nil or 25 kg ha -1 P 2 O 5 ) ; (ii) grazing severity (0.8 or 1.7 sheep ha -1 ); (iii) pre-existing growth conditions as defined by initial biomass (low or high); (iv) pre-existing stone cover (low or high); (v) final stone cover, modified by the addition or removal of stone to 20% or 80% stone cover; and (vi) experimental protection or non-protection from grazing. 2. 127 species were present, 56 of which were legumes, 21 grasses and 50 other species. The most common species were Trifolium campestre, T. tomentosum, T. stellatum and several species of Bromus and Avena. Overall, the frequency of only a minority of species was changed by environmental differences. 3. Initial growth conditions (as measured by initial biomass) most affected subsequent performance, although the effect was less marked in the second year. Pre-existing stone cover also resulted in large differences in subsequent growth, greater stone cover reducing growth, probably because it was associated with shallow soil and low soil fertility. Experimental addition of stones increased biomass, probably because the stones protected the vegetation from grazing. Individual species differed in their response to both pre-existing and added stone cover, the most frequent species being the most affected. High stocking rate reduced the biomass of most species, and application of P 2 O 1 increased it. Protection from grazing increased plant cover but individual species differed in their response. An abundance of stones was not necessarily harmful, and some species were favoured by their presence. 4. It is concluded that Mediterranean grasslands are less fragile than they appear since they have mechanisms that buffer them from environmental change. These mechanisms include the presence of a long-lived seed bank and certain adaptations such as the production of abundant small seeds and early flowering, but continued over-grazing clearly results in degradation.

Meroplankton dynamics in a saline, turbulent, turbid shallow lake (Neusiedlersee, Austria and Hungary)

Phytoplankton species composition, horizontal distribution, seasonal- and long-term dynamics are investigated in relation to some environmental factors, based on about 700 samples taken between 1968 and 1992 in the shallow, turbid, turbulent, saline Neusiedlersee (Austria/Hungary). We deduced: 1. The phytoplankton is relatively poor in species which is attributable to high salinity and turbidity. Blue-green algae of picoalgal size, meroplanktonic diatoms, green algae either with gelee or elongated form are the most important groups in the plankton; 2. No consequent horizontal differences in the distribution of phytoplankton biomass were found; the high contribution of diatoms (69%) and green algae (22%) is characteristic; 3. Despite the low percentage contribution (0.54%) of phytoplankton dry weight in total seston, the two variables correlate closely because of simultaneous resuspension after wind actions. The prevalence of both low phytoplankton/seston ratio and significant correlation between these two variables is indicative to the presence of a meroplankton; 4. Phytoplankton biomass, especially that of diatoms, varies within wide limits in the short term as a combined effect of growth/loss, transport by horizontal water currents and periodic resuspension from the sediment surface. Diatoms like Fragilaria, Surirella and Campylodiscus are involved especially. Parameters of population dynamics (growth rate, annual cycles, length of stationary phases, standing crop) were estimated based on moving averages. Growth rates were smaller than those of ‘normal’ planktonic species; however, the similarities of seasonal pattern suggest that the carrying capacity of the lake is very constant; 5. Picoalgal biomass is very high in the lake; its contribution to total biomass can exceed 75%, especially in spring. The large cellular chlorophyll a content of Neusiedlersee’s phytoplankton can most probably be explained by this high picoalgal standing crop, which is not included in the routine biomass estimations; 6. Concerning long-term changes of phytoplankton, periodic appearances and disappearances are very characteristic. Annual average biomass of most species is growing for several (3–5) years, then declining with a similar rate and these periods are recurrent. Climatic drying-out periods, during which water level lowers, conductivity increases, nutrients and their ratios change following trend-like periodicities, and they are supposed to be responsible for the observed longterm periodicity of dominant species. An increased nutrient load in the seventies was superimposed on this cyclicity; 7. Most of the species can be found in smaller or larger amounts in the littoral microhabitats (canals, inner ponds) of the lake in periods when they are absent or very rare in the open water. Thus, these littoral microhabitats play a very important role in the survival and recruitment of planktonic populations to the open water.

An index of biotic integrity to assess biological impacts of salmonid farm effluents on receiving waters

A major issue for water resource management is the assessment of environmental degradation of lotic ecosystems. In order to quantify the extent of resource degradation resulting from anthropogenic disturbances, a fish-based index, the Index of Biotic Integrity (IBI), has been used throughout North America and recently in Europe. The IBI is based on the assumption that fish assemblage attributes change in a characteristic fashion with stream degradation. In this study, using data from 1979 to 1991, we analysed the impact of 9 salmonid farm effluents on fish assemblages in some Brittany streams. Annual production of these farms varied between 2 and 300 tons. The data were first computed using a principal components analysis. Ordination of the points indicated longitudinal changes in fish assemblages from upstream to downstream and separated sites sampled upstream from sites sampled downstream from the fish farms. Depending on stream size, we found, downstream from trout farms, an increase in both density and biomass of most species, extirpation of sensitive ones ( Cottus gobio L.), and appearance of pollution-tolerant ( Rutilus rutilus L.) and exotic forms ( Oncorhynchus mykiss W.). Finally, we modified the IBI and compared it with chemical variables to illustrate how this index can be applied to quantify disturbances of the quality of stream water induced by fish farms. This IBI, based on 10 fish assemblage attributes, showed close agreement with these independent chemical measurements.