What would an underwater farm look like in a freshwater ecosystem?
September 25, 2016 1:13 PM   Subscribe

I've been hearing a lot of interesting stuff lately about kelp/seaweed farming, which often incorporates oysters, mussels, etc. Is a practical analogue for freshwater ecosystems possible?

The kelp farms are interesting because they're (allegedly) zero-input (no fertilizers) -- because the crops are providing an ecological benefit by extracting some of the excess nitrogen that's polluting the seawater. They're also low-impact or positive-impact on the seascape: farmed areas can be used simultaneously for recreation, fishing, and other commercial uses. Along with the farms focused on food production, some kelp farms in polluted areas are started purely for bioremediation purposes.

Which leads to my question for all you freshwater ecologists (and armchair ecologists) out there: Is something like this possible/practical in the Great Lakes, for food production and/or bioremediation? I've read that most freshwater algae are toxic. Are there any edible species? Could they be made tasty? What about native shellfish? If any are edible/tasty, would we have to do significant bioremediation before Great Lakes shellfish and/or freshwater vegetables would be safe to eat? I'm curious about eating invasive species, too, but from what I've read zebra mussels are inconveniently small and are listed as "not recommended" for consumption because of pollution issues.
posted by cnidaria to Science & Nature (10 answers total) 8 users marked this as a favorite
 
The Great Lakes area does have the largest biodiversity of mollosks in the world, I believe, with upwards of 300 species.

However, most varieties are slow growing or tiny, and in the wild most of them are threatened and protected. Harvesters even have a limit on the number of shells they can possess (and that number is just 4 for many Mississippi species).
And yes, zebra mussels are tiny and often encrust larger local mussels.

In the past mollusks were so abundant they were harvested by the hundreds of thousands to create mother of pearl buttons and that was the beginning of the demise of the populations on the Mississippi in conjunction with industrialization of the river.

While it's not native species, there is a business in the Upper Midwest raising food through aquaponics. Tilapia are farmed and produce as well.

Urban Fish Farm
posted by littlewater at 1:43 PM on September 25, 2016 [2 favorites]


littlewater has noted some of the logistical reasons it wouldn't work so well in the Great Lakes. The most important thing I would point to is the problem of scale. Oceans cover around 75% of the earth's surface, and 99% of the earth's water is saltwater. Most of the non-saltwater is either frozen in icecaps and glaciers or in groundwater. Surface freshwater makes up around 0.005% of the water on earth, and some of that is horribly polluted.

In addition to all of the logistical reasons, there are serious conservation reasons for not turning our tiny fraction of surface freshwater into agro-factories. Many freshwater species are endemic, meaning they are found only in a very small area and they would presumably not survive this farming. More selfishly, our freshwater systems also provide ecosystem services, including recreational uses like swimming, boating, and recreational fishing and vital uses like providing our drinking water and processing our post-treatment wastewater, that would be lost.

I would echo littlewater as well that aquaponics is a much more interesting freshwater application of what you're discussing. It is popping up all over in the country in places like former K-marts, providing hydroponic lettuce and tomatoes and tilapia, especially.
posted by hydropsyche at 2:38 PM on September 25, 2016 [4 favorites]


I'm hoping specifically to hear whether there are tasty/edible freshwater vegetables at all. I'm familiar with lots of marine greens from sea kayaking but I've never heard of any freshwater edibles.

From what I've listened to and read about kelp farming (though it could be excessively rosy) ecosystem services aren't lost. Swimming, boating, fishing, and recreation are still totally available in those areas -- the farming doesn't disrupt that. And recreational fishing in particular is improved. (Marine kelp farms are also a winter crop, which means you're unlikely to be swimming anyway -- but you could swim in season if you chose.) Also, I've seen conservation arguments that they actually *improve* local threatened ecology, both by providing habitat and directly reducing nitrogen runoff pollution by absorbing that nitrogen. Could be boosterism, but maybe not. I wouldn't dismiss it out of hand, especially in the context of working in tandem with marine reserves.

Are there reasons you couldn't conscientiously raise native species in an ag context in a way that supported biodiversity rather than hurting it? Small and slow-growing seem like the biggest ones. You could integrate them but not eat them.

I'm curious to see an analysis of aquaponics in terms of BTU input. I've seen a a very cool indoor farm in Michigan (http://www.greenspiritfarms.com) using targeted LED spectrums to efficiently grow greens (no fish). No pesticides and no long-distance transportation are a big deal, carbon- and pollution-wise. But I've also wondered whether its overall efficiency for the heat and light input required might depend on cheap Michigan nuclear power.
posted by cnidaria at 2:57 PM on September 25, 2016


Of course there are freshwater crops such as wild rice and cranberries.

Wild rice in Minnesota is tightly regulated. It's a wild crop, not a cultivated crop, and harvesting must be done with a license in the traditional way.

I know very little about cranberry production but it doesn't seem like the kind of crop that plays well with other things.

Probably the biggest hurdle to this is economic and regulatory. The cost to purchase the amount of lake and lakeshore to have enough space for this activity would probably be in the millions. Food output could never pay that mortgage.
And the activity may be prohibited in many areas, as mentioned, the harvest of mollusks and wild rice is tightly regulated. Lakes are temperamental and if I owned lakeshore on a lake where a fellow lakeshore owner were proposing some form of farming I would strongly oppose it. I think the risks to the balance of the lake would be serious.

However, setting up this kind of aquaponics is interesting, but native species are likely too fussy and fickle to cooperate.
posted by littlewater at 3:25 PM on September 25, 2016 [1 favorite]


I'm hoping specifically to hear whether there are tasty/edible freshwater vegetables at all. I'm familiar with lots of marine greens from sea kayaking but I've never heard of any freshwater edibles.

Watercress would be an example. Rice would probably count as well, and there are many others -- googling "edible water plants" or a similar phrase will get you lots of examples.
posted by Dip Flash at 3:25 PM on September 25, 2016


Definitely armchair ecologist here. As someone who has lived on the Great Lakes throughout my life, I try to follow ecology issues related to them as a nonscientist, because I think I should be pretty aware of what's happening with this incredible freshwater system.

So, if any of this helps:

from what I've read zebra mussels are inconveniently small and are listed as "not recommended" for consumption because of pollution issues.

Along with siltation, the zebra mussel has squeezed out the northern riffleshell in the Great Lakes system. It is listed as endangered.

The University of Guelph has a pretty extensive food science/agriculture faculty - here's some older commentary on aquaculture in Ontario:

Overview of Aquaculture in Ontario (pdf, 1997)

From a little earlier this year:

Lake Huron’s 9 Aquaculture Farms Drawn Into Michigan Legislative Furor:
A series of eight bills, six in favor of aquaculture in the Great Lakes and two opposed, were introduced in the Michigan legislature over the past eight months. The flurry of lawmaking was touched off by two proposals to farm fish in the Michigan waters of the Great Lakes, a notion that a state task force recommended the state not pursue earlier this year. Currently, no aquaculture facilities are licensed in the U.S. waters of the lakes, and they are illegal according to Michigan law. The bills, all of which are pending in committee, could change that.
posted by mandolin conspiracy at 3:37 PM on September 25, 2016 [2 favorites]


You might want to check out Minnesota Sea Grant for info as well.
posted by mandolin conspiracy at 3:46 PM on September 25, 2016 [1 favorite]


Cranberries don't pass your requirement. Wikipedia says:
A common misconception about cranberry production is that the beds remain flooded throughout the year. During the growing season cranberry beds are not flooded, but are irrigated regularly to maintain soil moisture. Beds are flooded in the autumn to facilitate harvest and again during the winter to protect against low temperatures.
It's kind of the opposite of rice, which does most of its growing in flooded fields, which are dried out just prior to harvest.
posted by Chocolate Pickle at 8:39 PM on September 25, 2016


The wikipedia article about rice says that Cajun rice farmers also use their fields to cultivate crayfish while the rice is growing. That sounds like the kind of thing you're looking for.
posted by Chocolate Pickle at 11:55 PM on September 25, 2016 [1 favorite]


Wasabi grows in streams, but it's reportedly "difficult to cultivate".
posted by Joe in Australia at 2:19 AM on September 26, 2016


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