Clearance Rates of Crustacean Macrofiltrators: The Nature ofin situ Rate Depressions in a Fertilized Oligotrophic Lake in the Kuokkel Area, Northern Sweden

• Published in: Internationale Revue der gesamten Hydrobiologie und Hydrographie
• Main Author: Persson, Gunnar
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 1985
• Subjects: Northern Sweden
• Online Access: http://dx.doi.org/10.1002/iroh.19850700304; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2Firoh.19850700304; https://onlinelibrary.wiley.com/doi/pdf/10.1002/iroh.19850700304

Abstract Lake seston labelled by 14 CO 2 , 14 C‐acetate and 32 ‐PO 4 in parallel was used in zooplankton feeding experiments and checked for size distribution of the labelled particulates. The in situ experiments were made to find out if depressed Eudiaptomus and Holopedium clearance rates, in an artificially fertilized lake where seston was dominated by μ‐algae, were due to low retention of such algae. Addition of a labelled reference alga ( Chlamydomonas sp.) was used to find out if high food concentrations (above the Incipient Limiting Concentration) or toxins caused the depressions. Clearance rates mostly ranked highest for CO 2 ‐labelled seston followed by 32 P and 14 C‐acetate labelled seston, reflecting approximately the size distributions of the labelled food. Clearance rates for the added reference alga were high and similar in the fertilized lake and in an oligotrophic reference lake. It was concluded that the detected “rate depression” could be explained purely by poor retention of small particles (passive size selection) by the crustaceans studied, but that active food selection offers optional explanations to the experimental results.