Zoobenthic Biomass Research Articles

The distribution of benthic invertebrates along a natural turbidity gradient in Lake Temiskaming, Ontario-Quebec

Lake Temiskaming, a rift valley lake on the Ontario-Quebec border, exhibits a permanent gradient of turbidity due to tributary streams which cut through clay deposits to the north of the lake. Concentrations of total phosphorus (TP) also decreased from north to south, with values suggesting mesotrophic conditions. Concentrations of chlorophyll a were characteristic of oligotrophic lakes and showed little relationship to either turbidity or TP. Large numbers of Tubificidae were found at our northernmost sampling station at a depth of 50 m, probably reflecting the localized impact of allochthonous organic matter introduced by a tributary stream. Numerical abundance of the benthic fauna was much lower and did not vary significantly among the six more southerly 50 m stations, but biomass declined from north to south as Heterotrissocladius oliveri relaced Pontoporeia hoyi. Numerical abundance did not differ significantly among stations at depths of 10 m, but biomass decreased from north to south reflecting the distributions of the largest species, Hexagenia sp. and P. hoyi. Intensive sampling on two transects showed that maximum numbers of invertebrates occurred in the profundal zone. While these results are consistent with the correlation between TP and zoobenthic biomass reported by other investigators, size selective predation by fish may also be important in controlling the distribution of benthic invertebrates in Lake Temiskaming.

Downstream Effects of Intermittent Power Generation

Intermittent power generation creates frequent and dramatic discharge peaks combined with intervening extremely low water conditions. Whereas no alterations were found in the qualitative composition of zoobenthos, the decrease in abundance and biomass may amount up to 95%. The mismatch between the hydrography of surface water and groundwater might well be a cause of the detrimental effects of frequent and artificially created spates. The drastic reduction of zoobenthic biomass affects not only fish production but minimizes self-purification processes as well. Until tributaries diminish the effects of intermittent power generation, the river is reduced to a mere transport vehicle.

Biomass and trophic structure of the macrobenthos in the south-west lagoon of New Caledonia

The biomass of the macrobenthic communities of the southwest lagoon of New Caledonia is analysed with special reference to tropical soft-bottom assemblages. The samples were obtained in 1986 from 350 Smith-McIntyre grabs as well as by diving over an area of 3 500 m2, and covered a wide size-range of benthic organisms. The classification of the biomass data into taxonomic groups revealed the following: (1) a zoobenthic biomass (mean=13 g ash-free dry wt m-2) that is high compared to values previously published for tropical systems, but fairly low compared to those recorded for medium and high latitudes; (2) a large macrophytic biomass (45% of ash-free dry wt); (3) dominance by weight of sponges, molluscs and cnidarians over the other faunal groups. The distribution of the biomass among the trophic groups revealed the following: (1) the dominance by weight of suspension-feeders, which account for 67% of the total zoobenthic ash-free dry wt; (2) the absence of trophic group amensalism between filter-feeders and deposit-feeders whatever the degree of bottom muddiness; (3) the existence of a relationship between the biomass of surface deposit-feeders and ATP at the surface layer of the sediment, suggesting that this group feeds preferentially on living particles. Differences in trophic structure between the muddy-bottom, greysand and white-sand communities of the lagoon reflect the functional characteristics of each bottom type.

Littoral Zoobenthic Biomass in Lakes, and Its Relationship to Physical, Chemical, and Trophic Factors

The hypothesis that littoral morphometry exerts a strong effect on zoobenthic biomass was tested in Lake Memphremagog, Quebec–Vermont, by regression analysis of the relationship between littoral zoobenthic biomass and littoral slope, exposure (Lake area visible from sampling site), and trophic status (micrograms of chlorophyll a per litre). Eighty-one percent of the variance in Log littoral zoobenthic biomass (LZB) could be explained by[Formula: see text]When the predictions from this relationship were compared with littoral zoobenthos estimates from other lakes, residuals were positively correlated with the calcium concentration of the water (r = 0.41) and negatively correlated with the chloride concentration (r = −0.51). The regression equation obtained for all of the sites was[Formula: see text]and explained 80% of the variation in Log LZB. Sites situated within deltas from stream inflows did not differ significantly from these that did not (ANCOVA), indicating that coarse allochthonous input from these fluvial sources was not a major factor determining littoral zoobenthic biomass in these lakes.

Empirical Models for Zoobenthic Biomass in Lakes

Estimates of macrozoobenthos from the literature were regressed against a series of limnological variables to yield empirical models for zoobenthic biomass in the profundal, sublittoral, and littoral zones of lakes. Variables indicative of phytoplankton biomass (chlorophyll concentration, total phosphorus concentration, and Secchi disk transparency) explained between 14 and 57% of the variance of zoobenthic biomass ((g/m2)0.1). Other factors such as humic colour, morphometry (slope, mean depth, ratio of mean to maximum depth, and lake area), and mean annual air temperature substantially increased the amount of explained variance. In the profundal and sublittoral zones, the best models explain 70% of the variance in zoobenthic biomass. Littoral zone models explained less than 50%, and this deficiency was attributed to sampling difficulties and to high local variability of slope and wave exposure in the littoral zone.

The Zoobenthic Biomass in the Southern Baltic

The Zoobenthic Biomass in the Southern Baltic