The Benthic Quality Index to Assess Water Quality of Lakes May Be Affected by Confounding Environmental Features

Abstract

To assess if environmental differences other than water quality may affect the outcome of the Benthic Quality Index, a comparison of the application of four different methods (Benthic Quality Index—BQIES, Lake Habitat Modification Score—LHMS, Lake Habitat Quality Assessment—LHQA and Organisation for Economic Co-operation and Development—OECD) used to classify the lake ecological and hydro-morphological status of 10 Italian lakes was performed. Five lakes were natural and five were reservoirs belonging to both Alpine and Mediterranean Ecoregions. The 10 lakes were sampled using the Water Framework Directive compliant standardized national protocol, which includes sampling soft sediment in the littoral, sublittoral and deep layers along transects with a grab of 225 cm2 during spring and autumn. The application of Generalised Linear Mixed Effect Models both at the lake level and at the single station of each lake highlighted that, at the lake level, no significant correlations existed between any couple of hydro-morphological, ecological and trophic status assessments, with each metric representing a different facet of human impact on the environment. At the single site level, we found significant effects of depth on the metrics of biodiversity. The best approximation of single-site macroinvertebrates diversity among the metrics of overall lake quality was with the LHMS, but not with the BQIES. Our hypotheses that lake macroinvertebrates assemblages depend also on other potential confounding variables of habitat degradation and intrinsic differences between lakes were confirmed, with depth playing a major role. Therefore, the assessment of lakes with different depths may produce different whole-lake BQIES values, only because of the effect of depth gradient and not because of differences in lake quality.

Factors Controlling Morphotaxa Distributions of Diptera Chironomidae in Freshwaters

“…The reason is that a species responds jointly to oxygen, temperature, phosphorous, water velocity, and substratum, that is, a too-great number of factors, and the emphasis on a particular factor may be more bound to the factors included in the model tested than to a true species preference for a factor. This is critical in testing the validity of biotic indexes in assessing the ecological status of water bodies because the interactions between different environmental factors of natural and anthropogenic origin may give contrasting results [73].…”

Response of Chironomids to Key Environmental Factors: Perspective for Biomonitoring

“…In conclusion, the key factors separating Chironomid species are confirmed to be substrate type, current velocity, water temperature, dissolved oxygen, conductivity, and nutrients, but these factors are differently related in various situations and anthropogenic stress and can contribute to creating other more complex interactions [ 15 ].…”

“…It is well known that different Chironomid species colonize different river reaches and lake types, suggesting the existence of krenal, rhithral, and potamal species in running waters, and littoral, sublittoral and profundal species in lakes [ 2 , 4 ]. In fact, species distribution can be easily related to a few environmental factors such as substrate type, habitat heterogeneity or alteration [ 5 , 6 , 7 ], distance from the source or mouth [ 8 ], current velocity [ 9 ], water temperature [ 5 , 10 ], lake depth [ 11 , 12 , 13 ], conductivity [ 2 , 4 ], salinity [ 5 ], oxygen content [ 5 , 14 , 15 ], pH [ 11 ], water quality [ 6 ], submerged plants [ 11 ], sediments organic matter content [ 10 ]. This result was evident in running waters just one century ago, with Orthocladiini and Tanytarsini dominating the upper reaches of rivers and Chironomini in the lower reaches.…”

Response of Chironomids to Key Environmental Factors: Perspective for Biomonitoring

“…In conclusion, the key factors separating Chironomid species are confirmed to be substrate, current velocity, water temperature, dissolved oxygen, conductivity, nutrients, but these factors are differently related in various situations and anthropogenic stress can contribute in creating other more complex interactions [9].…”

“…Different environmental factors were considered as responsible of Chironomids distribution. There is a huge number of contributions to this topic; temperature, salinity and oxygen [4], habitat heterogeneity and water quality [5], water temperature [6], submerged plants, sediments organic matter, distance from the mouth of river, pH [7], oxygen [8,9], depth in lakes [10,11,12] were considered key factors responsible of fauna composition.…”