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

Abstract

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 oliven 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.

Drivers of Abundance and Community Composition of Benthic Macroinvertebrates in Ottawa River Sediment near Chalk River Laboratories

“…In agreement with the results of this study, the most common invertebrate taxa observed in the upstream Lake Temiskaming benthic zone (at 10 m depth) included Chironomidae (Procladius, Tanytarsus and Polypedilum), Oligochaeta (Tubifex tubifex) and Hexagenia [36]. Our estimates of invertebrate biomass in Ottawa River sediment (0.1-2.5 g·m -2 ) are considerably lower than those for the Lake Temiskaming reach of the Ottawa River (1.9-17.3 g·m -2 ) [36], likely because we sampled the Ottawa River in November and Lake Temiskaming was sampled in May through August, when pre-emergence biomass is generally at its highest [42,43].…”

“…In the only previous study on the benthic invertebrate distribution in the Ottawa River near CRL, Rigler [15] found that Hexagenia was one of the most abundant benthic invertebrate taxa at depths from < 1-16 m, ranging from 10-20 individuals per m 2 . Hexagenia are also an important component of the Lake Temiskaming benthic community, upstream from Chalk River, ranging from 25-103 individuals·m -2 [36]. In this study, we found Hexagenia densities to be similar, ranging from 0-131 individuals·m -2 .…”

“…Sallenave and Barton [36] investigated the benthic invertebrate community in the Lake Temiskaming section of the Ottawa River and found that mean invertebrate abundance ranged from approximately 800-2,000 individuals·m -2 (at 10 m depth), compared to the estimates of 350-1,008 individuals·m -2 (at 15 m depth) observed in this study. In agreement with the results of this study, the most common invertebrate taxa observed in the upstream Lake Temiskaming benthic zone (at 10 m depth) included Chironomidae (Procladius, Tanytarsus and Polypedilum), Oligochaeta (Tubifex tubifex) and Hexagenia [36].…”

“…Sallenave and Barton [36] investigated the benthic invertebrate community in the Lake Temiskaming section of the Ottawa River and found that mean invertebrate abundance ranged from approximately 800-2,000 individuals·m -2 (at 10 m depth), compared to the estimates of 350-1,008 individuals·m -2 (at 15 m depth) observed in this study. In agreement with the results of this study, the most common invertebrate taxa observed in the upstream Lake Temiskaming benthic zone (at 10 m depth) included Chironomidae (Procladius, Tanytarsus and Polypedilum), Oligochaeta (Tubifex tubifex) and Hexagenia [36]. Our estimates of invertebrate biomass in Ottawa River sediment (0.1-2.5 g·m -2 ) are considerably lower than those for the Lake Temiskaming reach of the Ottawa River (1.9-17.3 g·m -2 ) [36], likely because we sampled the Ottawa River in November and Lake Temiskaming was sampled in May through August, when pre-emergence biomass is generally at its highest [42,43].…”

“…Hyland et al [28] take a more conservative approach, suggesting organic impairment at 3.5% sediment organic content. Sediment organic content in Lake Temiskaming, 180 km upstream from CRL (Figure 1), ranged from 3-6% [36], lower than in the CRL section of the Ottawa River where it ranged from 5-15%. This is likely because the physical and hydrological properties of the CRL section of the Ottawa River create a depositional pool along the broader river network, in which particulate and organics settle out of the water column and accumulate on the bottom.…”