Filter Feeders: Cleaning up the Water

In a video regarding shellfish farming, the now infamous “they clean the water” claim is made. Two 1-gallon glass containers are shown side by side. They each contain seawater and “300,000 cells of algae/mL.” One container holds just the seawater and the other includes 60 manila clams suspended in a net. After 28 minutes, the water in the container with the manila clams is obviously clearer.

The Water’s Clearer – But Is it Cleaner?
 
Actually the water was never “dirty” and the clams are not cleaning anything – they are eating. Like all filter feeders, they eat phytoplankton (minute plants). They also ingest other suspended matter including minute animals (zooplankton), fish larvae and other larvae, and anything else small enough to pass through their siphons.

To rephrase an old saying… “What goes in must come out.” That’s right, they poop! Scientists don’t call it poop – they call it biodeposits (the process is called biodeposition). The biodeposits contain feces (waste from digested plant matter) and pseudofeces (dead zooplankton and other non-digestible matter).

What is not shown on the video is the bottom of the tank where biodeposits would have accumulated. What happens to these biodeposits? It really depends on the amount of accumulated biodeposits. At low density they are decomposed via an anaerobic bacterial process (one that does not use oxygen). This process also converts dissolved nitrogen into nitrogen gas that bubbles up and into the air (called denitrification). This is a positive process since one of the issues in our saltwater areas is an excess of dissolved nitrogen.

However, if the density of biodeposits gets too high, the “good bacteria” are overwhelmed and the decomposition changes to an aerobic process (uses up dissolved oxygen in the water column). Instead of denitrification, oxygen is depleted and nasty stuff like Beggiatoa is formed. Scientifically speaking, “Beggiatoa can grow chemoorgano-heterotrophically by oxidizing organic compounds to carbon dioxide in the presence of oxygen.”

So the question of positive impact versus negative impact depends on the density of the biodeposits. The density of biodeposits is related to the density of animals and the speed of the current. Shellfish planted in low-densites, and in high current almost never cause problems. However, aquaculture often places animals in densities 10 to 100 times greater than found in nature. In addition, shellfish are often grown in protected coves and inlets that have very slow currents. Thus the likelihood of high-density related biodeposition problems associated with aquaculture is significant.

Sharing the Wealth
 
As the video points out, filter feeders eat a lot phytoplankton (an adult oyster can filter 65 gallons/day). Unfortunately, filter feeders are not the only consumers of phytoplankton. The truth is EVERYTHING in the sound is dependent, either directly or indirectly on phytoplankton to survive. This ranges from microscopic zooplankton, up to and including the Orca.

It is common to hear shellfish people (and some state agency people) say that there is an abundance of phytoplankton in Puget Sound. They point to algae blooms as evidence of this. The truth however is there is no science that we know of that substantiates this claim. Yes, there are algae blooms in some parts of the sound during some times of the year, but this really isn’t the issue. The issue is what happens in small, protected coves and inlets where currents are low, when the shellfish farmer places 10 to 100 time more animals than found in nature on the shoreline? What happens to the food web in these areas? What if these areas also support the spawning activities of forage fish (including their larvae).

Summary
 
“Cleaning the Water” is a misleading public relations term that the shellfish industry has used for decades to justify its expansion. It is time for regulators to sit up and take into account the density and placement of shellfish operations to insure that the shoreline ecosystem is not harmed.

Shoreline Science

For many, understanding the environmental issues of South Puget Sound’s important shorelines is a bit difficult. Harry Branch, who has a master’s degree in Environmental Studies, has written an excellent letter to the Thurston County Commissioners describing the issues. He has done an great job of describing the situation in a language that is easier for the non-scientist to understand.

We present Harry’s letter below:

Letter from Harry Branch to Thurston County – Aquaculture/Shoreline Development

The County is correct that geoduck farming on area beaches is Shoreline Development. Any alteration of structure that impacts ecological function is development.

Taylor Shellfish has put forth a number of studies claiming that water quality, the marine food chain, water circulation and native species will not be effected by expanded shellfish cultivation. Studies also claim that increased shellfish production will remove a large percentage of the nitrogen introduced into the environment by humans. Nitrogen is suggested to be a major water quality problem by over-fertilizing algal blooms that die off and create anoxic conditions.

Nitrogen and sunlight are also the essential building blocks of life. Nitrogen is utilized by phytoplankton (primary production) which is then consumed by  zooplankton and so on up the food web.  This happens best in shallow water with persistent patterns of circulation, the basic estuary. In South Puget Sound we've altered three out of four estuaries (don't forget the streams). Often the entire estuary is fed through a long pipe and dissolved oxygen and other basic parameters take a dive. The problem as often as not is changes in structure to tide flats, salt marsh and the upper beach rather than the introduction of too many nutrients. (See the spring edition of Green Pages for a more in-depth look at this question).

Shellfish don't eat nitrogen, they eat phytoplankton that has consumed nitrogen. Because phytoplankton reproduce rapidly, there is only a temporary lag in abundance. Taylor's studies thoroughly evaluate the potential effects on phytoplankton abundance spatially, seasonally and diurnally. The limiting factor in a typical system is primary production. The rationale is that by assessing the impact on primary production we can predict impacts on the entire food web.

Well, that's poppycock. Mussels don't just eat phytoplankton, they eat zooplankton, from tiny protozoa that mimic phytoplankton to larger fish larvae, tiny insect-like babies that will become larger fish, crabs, barnacles and so on. Nearly all fish consume zooplankton during their larval phase and some fish continue to do so their entire lives. A single herring may consume thousands of copepods in a single day. Larger zooplankton are important food for forage fish and growing fish larvae. They link primary producers with larger, higher tropic level animals. Because zooplankton reproduction tends to lag phytoplankton reproduction, the reduction in nitrogen contained in phytoplankton is probably more than offset by a reduction in herbivores such as copepods. Copepods, probably the most plentiful creatures on earth, are the natural control for phytoplankton; they maintain balance in the system. The only benefit of large scale shellfish cultivation, if one can consider it a benefit, is that phytoplankton, herbivores and secondary consumers, i.e. everything, is reduced.

Shellfish cultivation on area beaches without doubt impedes a host of important ecological processes including forage fish spawning. Virtually all native species, from ghost shrimp to macro-algae to diving ducks, are considered pests. This modus operandi runs antithetical to Ecosystem Based Management, the direction we are and must be heading.

Taylor suggests that water quality in Totten Inlet has been impacted by, among other things, humans over-harvesting shellfish. Since we haven't been assessing dissolved oxygen for very long, this theory is entirely conjecture. Concerning the most basic, physical parameters, Totten Inlet like much of Puget Sound and Hood Canal is a fjord. It's perfectly natural for the water column to be stratified and anoxic below a certain depth.

Taylor could make a better case that by over-harvesting resources and altering the structure of Puget Sound through dredging, filling and destroying almost all our estuaries, we damaged the ecosystem and shellfish growers are only filling an empty niche. But this would be a very disjointed weak argument as well. The sustainability of an ecosystem comprised of three kinds of bivalves is doubtful at best. Compacting and biological sameness create an environment where diseases can easily spread. Outside influences such as acidification pose additional risks. And if any species crashes there may be nothing to replace it except bacteria and perhaps jellyfish.

We don't know the economic potential of all the fisheries that could be developed through restoration and enhancement of Puget Sound's natural ecosystems. It seems likely that rockfish, flatfish, salmon, herring, smelt and shellfish in combination would be marvelously productive. Sadly, estuarine and nearshore structure continues to suffer the woes of development. But this is no reason to allow shellfish cultivation to completely ruin what's left. "Geoduck farm" sounds so benevolent. But this isn't anything like farming. If anything we're talking about feed lots.

My family owned the oldest vineyard in the State on Stretch island. They're house and my aunt's house next door overlooked Puget Sound. Not that long ago we could net herring and smelt with a rake, filling a small boat in short time. My father caught a 46 pound lingcod virtually off his front porch. Not these days. The beach was beautiful and enjoyed by all. I don't know if it is now covered with PVC and netting. If I find out that it is, my heart will sink. It must be very sad for people who live on the waterfront to have to witness this assault. If this isn't shoreline development, I don't know what is.

Thank you Thurston County for standing your ground on this important question. If I can be of any assistance, please let me know.

Harry Branch

Harry's Background

Harry Branch has a Masters Degree in Environmental Studies with a focus on marine reserves as a tool in fishery management. He has also served as a captain operating research vessels for agencies like NOAA. He's worked on sea otter catch and release efforts, bioassays, bird counts and other live science.

Aquaculture “Pests”

The video I Am The Puget Sound speaks to what the aquaculture industry refers to as pests:

I understand they've made a list of what they think are pests

But these are all my children so by nature I'll protest

The actual document that refers to the “pests” is titled Pest Management Strategic Plan for Bivalve in Oregon and Washington.

The question we have is: Who gave this industry the right to declare native and migratory animals in Puget Sound as “pests”?

As an interesting point of irony, several of the invasive species the aquaculture industry wants to control were introduced by the same aquaculture industry in the past.

Government Contact Information

If you would like to voice your concern about what is happening in the South Puget Sound, here are some contact points:

State Officials

• Governor Chris Gregoire
• Commissioner of Public Lands – Peter Goldmark
• Director, Washington Department of Ecology – Ted Sturdevan
• Find Your Legislator
• Senate Member E-mail List
• House of Representatives Member E-mail List

Thurston County

• Thurston County Commissioners

Pierce County

• Pat McCarthy, Pierce County Commissioner

Mason County

• Mason County Commissioners