engleski

Seasonal drift-benthos trends on a moss-covered tufa barrier within a karst barrage hydrosystem (Plitvice Lakes, Croatia)

Macroinvrtebrate drift and streambed material transport are very important for the redistribution of energy sources and habitat-building elements within lotic ecosystems. The objective of the present study was to examine seasonal drift-benthos trends of macroinvertebrates and organic/inorganic matter particles between barrier and pool habitats at a small spatial scale within a karst barrage hydrosystem (Plitvice Lakes). Benthos and drift were sampled seasonally between November 2006 and July 2007 at four sampling sampling sites representing barrier (B ; fast-flow velocity) and pool (P ; slow-flow velocity) habitats. During the entire study period, amounts of drifting macroinvertebrates, and organic and inorganic particles were significantly higher at barriers than in pools. In benthos, such barrier trend was found for moss only. Considering seasonal differences, benthos showed no significant trends, whereas in drift we found significantly higher loads of all measured items in autumn and winter than in other two seasons, but such trend was observed at barriers only. The quantities of organisms in benthos and drift greatly followed the respective trends of particulate organic and inorganic matter, especially moss. At both habitat types macroinvertebrate drift mostly presented a smaller proportion of total benthos faunal composition, although there were some taxa that occurred in drift or benthos only. In total (including benthos and drift samples), we found 63 taxa during the study - 5 of them were found only within pools, 38 only at barriers and 20 of them were found at both habitat types. The most dominant in both benthos and drift, were Oligochaeta, cladoceran Alona spp., Copepoda, and larval stages of coleopteran Riolus spp. and dipteran Simulium spp. Most of them belong to mobile, epiphytic and/or interstitial detritivores that most likely originated from the submerged aquatic vegetation (i.e., moss), floating leaf litter and/or sediments along our study reach, whereas cladoceran and copepod taxa likely originated from the upstream lake. The observed seasonality in the faunal drift-benthos composition (e.g., Cladocera increase in summer and autumn, Ephemeroptera decrease/absence in winter and spring), was likely a consequence of the seasonal food sourcing for individual taxa, and their particular life history traits. Our findings suggest that within the tufa-precipitating Plitvice Lakes hydrosystem: a) drift has a very important role in maintaining benthos structure and stability within the barrier and pool habitats ; b) tufa barriers are highly dynamic habitats, characterized by pronounced season-specific dislodgement of the benthic organisms and particulate matter, and effective moss-mediated macroinvertebrate dispersal ; c) the abundance of macroinvertebrates and the amounts of organic/ inorganic particles in drift are influenced not only by flow velocity and the seasonal lake discharges/ biocommunity dynamics, but also by the initial distribution of particles/organisms within benthos as well as by the life history traits of the individual benthic organisms.

tufa barriers; pools; moss; drift; benthic macrofauna; Plitvice Lakes

nije evidentirano