Postponing nutrient uptake by algae in ragworm culture

In the Province of Zeeland ragworms (Atilla virens) are farmed on large scale (6 ha) in open rectangular (flow through systems) ponds.  In April these ponds are stocked with ragworm larvae from a hatchery. The juveniles bury themselves in the sediment layer in the pond and are fed with feed pellets. Dependent on the market (bait for fishing or maturation feed for shrimp farming) market size ragworms are harvested after 7 – 20 months.

In previous research the possibilities to utilize waste water for algae culture was investigated, showing promising results. However, one of the main drawbacks is that much of the nutrients are immediately consumed by algae in the ponds preventing them to be available for specific algaeculture in the effluent of the ponds. If it’s possible to limit algaeculture in the ponds and delay uptake, nutrients may stay available. The idea is to add a substance to make the ponds turbid and thereby limiting light influx. One of the positive side effects would be the limitation of predation on the ragworms by birds. Birds can consume as much as 500 kg ragworms per pond per year. A higher turbidity of pond water is likely to prevent predation for a large part.

One position is available to do a quick scan on the different possible substances, involving lab-scale experiments to investigate the effect on ragworms. The main question would be which non-harmful and non-toxic substances can be used to increase turbidity and can easily be removed later in the process to prevent or postpone nutrient uptake by algae in the ponds without affecting ragworm condition and growth.

Research type: literature study, experiments (HZ laboratory).

Research level: Minor/internship (BSc. level)

Prerequisite: good understanding of biology/chemistry; good analytical skills; communicative;

Partners: several Small and Medium (Aquaculture) Enterprises, Flemish  knowledge partners, Province of Zeeland

Researcher involved: research group aquaculture (Michel Trommelen and Jouke Heringa)

Period: 2nd semester 2017-2018

Status: Open