Benthic Communities: Case Studies in Fiji and Canada Dr Edward Anderson Division of Marine Studies The University of the South Pacific (679)

Benthic Communities and Marine Pollution Benthic habitat classification based on sonic mapping of the seafloor does not complete an investigation of pollution. Coupled with this should be mapping of communities. Benthos, and particularly infauna, in sieve sizes macofauna (>200μm) and meiofauna (>64 μm) are most useful, because they must remain in the local area The apparatus for this is simple: a sediment grab, a way to separate the animals form the sediment, and a microscope. The problem is that benthic animals which are useful for determining pollution status are small, and their identification is difficult.

Useful for Pollution Studies – But Some Difficult to Identify Macrofauna Annelid Worms – Mostly Polychaetes and Oligochaetes Crustacea – Amphipods, Isopods, Crabs, Tanaids, Molluscs – Bivalves, Gastropods Echinoderns – Starfish, Ophiuroids, Urchins Many others Meiofauna Crustacea - Harpacticoid Copepods Nematodes Many others

Environmental Effect of Salmon Aquaculture in Net Pens The case study from Canada is an investigation of benthic recovery from pollution under net-pen culture of salmon. The pens are fed with pelletized fish meal. Waste meal and fish feces go to the bottom. In a small area of the ocean (typically 100m x 500m) the equivalent waste from a city of 250,000 is deposited.

Methods Identification Currents Sediment particle size H 2 S Visual

The study sites Eight recently fallowed sites sites were selected Site were chosen for suitable soft bottom, and a nearby reference site. Sites were visited in each year from 1991 to Primary sampling device: a Ponar grab. Sampling was from an outboard motor boat equipped with a hydraulic winch.

Small, But Effective

Example Study Sites ▲ Sansum Narrows : high current, 19m, course sand Tranquil Inlet: low current, 27m silt/sand ►

Community Structure We sampled 25 sites in triplicate for 2-4 years. 348 taxa were identified, most to species. The raw data: 19 pages of species identifications and counts. You don’t want to read this!

Alternatives Some form of summary is necessary. Some options: Univariate Diversity Multivariate Cluster analysis Factor analysis I will deal mostly with deversity

Best Measure of Diversity H’ takes into account both the number of species, and the distribution of species in that number where i is the i th species in order of abundance S is the total number of species P i is the proportion of individuals in the sample belonging to species i (the probability that an individual selected at random will be found to belong to species i (in other words, P i is just n i /N) n j is the abundance of species i N is the total number (abundance) of individuals in the sample

Main Result A diversity analysis showed that recovery time varied from 0 months at a high current site to 50 months at a low current site. Measurements of community diversity were confirmed by sediment particle size, H 2 S and current measurements.

High current Sand Shallow Low current Silt Deeper

Confirmations Measurements of community diversity were confirmed by sediment H 2 S, particle size and current measurements. The effects were confined within a few hundred meters of the net pens. The effects are reversible. High H 2 S accompanies pollution from oxygen consuming wastes, which are the major sources of marine pollution worldwide.

TRE and TRER, 1991 and 1993

Case Study in Suva The case study from Suva, Fiji is student work There were 460 students over the 14 years that either I or Dr Vikila Vuki ran the course. This is half of the class of 2006 in MS312, Marine Pollution

Measurements We measured pollution at Walu Bay, Draunibota Bay (Lami, near Suva) and at Kinoya sewage outfall. This study was repeated in most years from 2001 to 2010, with similar results. Pollution in Suva, and in particular Walu Bay, is not getting better.

Walu Bay Why Walu Bay? Near to USP Large area of soft bottom Similar depth Lots of pollution Local food processing Upstream industries Probable sewage (not from container ships)

H 2 S Hach Kit Test Preparation 15 ml of sediment sample. Add seawater Drop in an Alka Seltzer tabled. This will release CO2, and sparge out the H2S. Reaction In the vial cap, there is a filter paper impregnated with Lead Acetate – colorless and soluble Lead acetate is converted to lead sulfide by H2S, dark colour, insoluble

Hach Kit (continued) The filters are read by reference to a colour chart. The method is semi- quantitative. Fast No special equipment There are other methods – but they require special equipment or access to a laboratory or both.

Community Analysis CategoryTaxonD1D2C1C2B1B2A1A2 1 Polychaetes and other worms Pol Bivalves (clams) Biv Other molluscsOmo CrustaceaCru Forams Fish1 7Other N S H' H2SH2S

Results Benthos was completely absent at Station A, in the inner reaches of Walu Bay, H 2 S was high, bottom current very low. In the overlying water oxygen was near normal at the surface and also at 1m above bottom at all stations. At the entrance to Walu Bay, Station C, diversity and H 2 S content were near normal. At Station D, 450m offshore, they were normal.

Comparisons The study in Canada involved about one year of effort, spread over three years. The range covered was large. The analysis was very detailed. Several taxon experts were necessary. A manual for the identification of marine invertebrates is essential.

Comparisons (continued) The student effort was confined to two field sessions and four laboratory sessions None of the students had any experience in identifying marine invertebrates to the species level, for the taxa interest. We used a large mesh size (500μm versus 200μm for practical reasons. There is no manual. The method is robust.

End. Questions?