SECTION A: NEW WORK PLANS

EFFLUENTS AND POLLUTION

Collaborating Institution
Auburn University
Claude Boyd
Oscar Zelaya

Note: This work plan replaces the discontinued Education Development Component Eighth Work Plan activity HCD1B, "Create a CRSP Fellowship Program to Provide Appropriate Support for Graduate-Level Students." It appears here for the first time.

Objective
To measure changes in physical and chemical characteristics of pond water and soils in response to varying density of production and in the presence or absence of water recirculation.

Significance
Nutrient enrichment of pond waters is an essential management practice in aquaculture. However, the discharge of pond effluents may result in deterioration of the receiving waters. There is considerable interest in reducing the negative environmental impacts of aquaculture in Honduras. One of the most promising methods for reducing the environmental effects of pond aquaculture is to use water-recirculating systems to minimize the discharge of effluents.

Anticipated Benefits
This research will demonstrate if water recirculation may be used to prevent the use of water exchange and release of pond effluents during high-density pond culture of aquaculture species. The findings will allow a discussion of the feasibility of using water recirculation to minimize the discharge of pond effluents in aquaculture in Honduras, and the environmental implications of aquaculture with or without recirculation in Honduras. The findings will be of great benefit to those seeking ways of promoting environmentally responsible aquaculture in Honduras and other nations.

This research will also contribute to a better understanding of pond dynamics. As an investigation that makes up the thesis project of a CRSP-sponsored host country graduate student, this research will provide an environment for learning research techniques, sampling methods, and analytical protocol that will be very useful to the student and to his country.

Identification of Beneficiaries
Aquaculturists throughout Central America, the US, and other countries that experience water quality problems related to the discharge of aquaculture effluents.

Study Design
Site:Research ponds at the Claude Peteet Mariculture Center, Gulf Shores, Alabama.

Pond Facilities:12 ponds, each with a surface area of 1000 m² and an average depth of 1.2 m. The ponds have plastic liners covered with a 15-cm layer of soil.

Culture Period:21 weeks (7 May–30 September 1999).

Culture Species: Penaeus vannamei.

Stocking Rate:High-density ponds will be stocked at 50 postlarvae (PL) m^-2; low-density ponds at 25 PL m^-2.

Water Management:Ponds without water circulation will be filled and water added only to replace losses to evaporation. In recirculation ponds, water will be pumped from culture ponds to treatment ponds and then pumped back to the culture ponds. Water retention time in treatment ponds will be one week, and culture and treatment ponds have equal volume.

Other Inputs:A 35% protein pelleted feed will be purchased from Burris Feed Mill, Slidell, Louisiana. The feeding rates will increase as shrimp biomass increases according to a standard feeding table. Feeding trays will be used to prevent overfeeding.

Treatments(with three replications each) as follows:
High-density production with water recirculation
High-density production without water recirculation
Low-density production without water recirculation

Note: In the water recirculation treatment, three unstocked ponds of the same size as the production ponds were used as water treatment reservoirs for the recirculation system.

Sampling Plan:Water samples representing the surface 80-cm stratum will be taken weekly throughout the culture period with a water column sampler. Water analysis will be done the day after samples are taken for the following parameters: soluble reactive phosphorus, total phosphorus, total nitrogen, nitrites, nitrates, and total suspended solids. At least twice a month, fresh samples will be collected for biochemical oxygen demand and chlorophyll aanalysis.

Soil samples will be collected from 12 places in each pond before stocking and before harvesting. For each soil sampling, three consecutive levels from the surface are considered: the first 2.5 cm, the second 2.5 cm, and the level from 5 to 10 cm. The soil samples will be dried and stored. They will be analyzed between December 1999 and June 2000. The parameters for the soil analyses include pH, carbon, nitrogen, and sulfur. Soil respiration analysis will be run for the samples taken from the first 2.5-cm layer.

Statistical Methods and Hypotheses:Analysis of variance techniques will be used to determine if differences exist among treatments with respect to soil and water quality variables.

The null hypotheses are as follows: Water and bottom soil quality will not differ between high-density ponds with and without water circulation; water and bottom soil quality will not differ between low- and high-density ponds with or without water circulation; and water and bottom soils quality will not differ between high-density ponds with water recirculation and low-density ponds without recirculation.

Schedule
Soil and water sampling: 23 April to 30 September 1999
Laboratory analyses: 24 April 1999 to 30 June 2000
Data analysis: June 1999 to June 2000

Report Submission
Progress report due: 31 July 2000
Final deliverable (thesis) due: 30 March 2001