A plankton trap for exposed rocky intertidal shores

Abstract

This paper describes a passive Rocky Intertidal Plankton Trap (RIPT) that can be used in exposed rocky shores. The RIPT is light, simple to build, easy to install and inexpensive. It endures water velocities up to 7.7 m s-1 and provides an integration over time of the mero- and holo-plankton arriving at the rocky shore. Two sets of 4 traps were tested, over a period of 3 d, in 2 exposed rocky shores in central Chile. The RIPTs collected a total of 21 major plankton taxa ranging in size from 100 μm (bivalve larvae) to 2700 μm (Isopoda). The cumulative number of planktonic organisms collected per trap ranged between 123 and 215. Cylinders of dentist chalk attached inside and outside the RIPTs and specially designed RIPT-flowmeters permitted an evaluation of water flux and an approximation of the rate of water filtering through the RIPTs. Maximum water velocities on the intertidal platforms were determined with the use of an intertidal dynamometer.