Benthic Communities: Case Studies in Fiji and Canada

Benthic Communities: Case Studies in Fiji and Canada Dr Edward Anderson Division of Marine Studies The University of the South Pacific anderson_ed@usp.ac.fj (679) 323-2948

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 • H2S • 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 1994. • 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 Pi 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, Pi is just ni /N) nj 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, H2S and current measurements.

High current Sand Shallow Low current Silt Deeper

Confirmations • Measurements of community diversity were confirmed by sediment H2S, particle size and current measurements. • The effects were confined within a few hundred meters of the net pens. • The effects are reversible. • High H2S 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 VikilaVuki 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)

H2S 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

Results • Benthos was completely absent at Station A, in the inner reaches of Walu Bay, H2S 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 H2S 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?

Benthic Communities: Case Studies in Fiji and Canada