Preliminary investigation into the stimulation of phytoplankton photophysiology and growth by whale faeces

This study demonstrates that pygmy blue whale faeces stimulates the photosynthetic performance and growth of three marine phytoplankton species, Dunaliella tertiolecta, Chaetoceros pendulus and Phaeocystis antarctica. Photosynthetic and growth parameters were compared at four time-points over a 21day experiment with 6 different treatments: a positive control (F/2 culture media), a negative control (iron-deplete F/2 culture media), and four faecal treatments ranging from 4375 to 220,267μgfaecesl-1. At each time point, rapid light curves were generated using Pulse-Amplitude Modulated (PAM) fluorometry to obtain the parameters maximum quantum yield (FV/FM), maximum relative electron transport rate (rETRmax), and photosynthetic efficiency (α). Change in the relative abundance of microalgal cells and the concentration of chlorophyll a was also determined periodically for each species. The chlorophyte D. tertiolecta and the diatom C. pendulus both exhibited clear dose-dependent stimulation of photosynthetic and growth parameters within 7days of incubation. There was also a strong interaction between incubation period and treatment in C. pendulus cultures which may be indicative of nutrient exhaustion following faecally-stimulated growth. The growth response observed for P. antarctica was less variable with respect to faecal concentration. These findings are considered preliminary, but illustrate that whales are a potentially important means of marine nutrient recycling. © 2013 Elsevier B.V.