Biological base-line trials of an integrated plankton pumping system in Placentia Bay, Newfoundland

Abstract

Newfoundland's inshore waters continue to play an important role in the lives of many of its people. The shoreward portion may as a fishery reservoir influence species which contribute more than 70% of the landed value of commercial and sports fisheries. Yet the microbiota on which this reservoir is based has been a very neglected aspect of the island's marine biology. With the increase in coastal industrial development there is a greater potential for deterioration of this fragile and unfamiliar resource base. -- In this social context a portable plankton pumping system was designed, assembled, and evaluated. The first module, a commercial diaphragm pump delivers sea water to a surge-tank where temperature, salinity, conductivity and dissolved oxygen measurements are made. In the third module the water is filtered by gravity flow through four Nitex plankton filters sequentially arranged after which the water's volume is determined. -- Evaluation consisted of seventeen closely integrated field and laboratory experiments. Most of the field evaluation took place at Come by Chance adjacent to an oil refinery prior to its start-up operations. Several aspects of its operation and laboratory procedures were assessed. -- Electronic environmental sensors were evaluated against alternate methods. Of these only the dissolved oxygen sensor yielded statistically significant variations. The water meter's performance was well within the value assured by the manufacturer. The filter-cleaning procedures were satisfactory and sedimentation losses were not significant. -- To evaluate zooplankton catching efficiency a conical net was tied below the pump's intake and both were pulled simultaneously through the same water column. There was little pump damage to plankton. The pump captured more of the smaller forms while the net retained more of the larger. -- Together the net and the pump provided a means of gathering information on plankton numbers, diversity and their aqueous environment in a manner not previously demonstrated. Reduction of spatial and temporal displacement of the sampling devices increases the confidence one has in the conclusion that the numbers and diversity of plankton in the water column are more closely approximated by both devices together than by either operated singly.