426. Eelgrass Trials and Tribulations

February 7, 2015

Eelgrass is an underwater flowering plant that feeds and protects a significant numbers of estuarine and marine species. Like those many species, I, too, have a longstanding engagement with eelgrass in Taunton Bay, though unlike them, my life doesn’t depend on that engagement. I don’t live in it and don’t eat it.

But I do photograph great blue herons and Canada geese that feed in eelgrass meadows near low tide, as well as least sandpipers that glean amphipods (beach hoppers, scuds, and the like) from the wrack of dead leaves that break off from their grassy stems and wash up onshore at the end of the season. So, yes, like my other engagements with nature, eelgrass is part of my life because it’s part of my ongoing awareness.

For over twenty-five years, I have conducted aerial surveys of eelgrass in the bay at frequent intervals. The meadows vary in size from one year to the next because the conditions affecting their growth are never the same two years in a row.

In 2001, the meadows abruptly disappeared, leaf blades turning black, then breaking off their stems and floating away on the tide. Leaving fish nurseries without their usual protective thickets, Canada geese without fronds to graze, black ducks without periwinkles to dabble and upend for.

Shocking surprises get my attention because they trigger consciousness itself. Pleasant surprises do, too, but this was no pleasant surprise.

Eelgrass Dieback Disease, 2001

Eelgrass in the Throes of Dieback Disease, August 2001

This was a catastrophe for Taunton Bay, and I hadn’t seen it coming. If I had extrapolated the downward trend of rainfall in preceding years, I might have predicted the drought, but I noticed it only in hindsight. I wouldn’t have predicted the dieback because I didn’t know that the wasting disease responsible for the loss of eelgrass was usually held in check by the low salinity characteristic of estuaries where streamflow and snowmelt dilute the saltiness of incoming tides.

I spent years trying to grasp what had gone wrong, and by studying aerial photos, finally figured it was a one-two punch delivered by a season with the least rainfall in the region since precipitation records had been kept for over a hundred years. The higher than normal salinity favored the dieback disease, which knocked out the eelgrass.

 

Recovering Eelgrass Meadow

Eelgrass Recovering from Dieback Disease, June 2010

There were no sea lavender plants in 2001, either. What do eelgrass and sea lavender have in common? An absolute dependence on skywater. In the first case to keep salinity low so the wasting disease (which thrives in high salinity) wouldn’t take hold. In the second case, to maintain sufficient flow of water through the soil from shorelands into sandflats where sea lavender thrives.

It took some eight years for the meadows to recover to anywhere near their extent in the year before the drought. I could tell that eelgrass was beginning to come back when sprouts appeared in the shallow drainage channels across mudflats at the mouths of small streams. Of all places in the bay, that’s where salinity is lowest and most hostile to the wasting disease organism. A seed that settles there has a good chance of taking hold.

 

Eelgrass Up-Close and Personal

Healthy Blades of Eelgrass at Low Tide

Eelgrass meadows disappeared again in 2013 as abruptly as they did in 2001, for an entirely different reason. Here again there were warning signs, this time unusually high turbidity two years in a row, but no one could figure out why bay waters were so cloudy. Was it due to mussel dragging in Frenchman Bay? Hand-raking mussels in Taunton Bay? As it turned out, it was due to green crabs.

No one suspected that the unusually warm winter of 2012-2013 would spur a bloom in invasive green crab populations, or that that bloom would affect eelgrass. But that’s what happened. In 2013, green crabs were everywhere. I saw a great many every time I walked along the shore. Lobster pots containing hundreds of green crabs were hauled up, attracted by the bait in each trap. I had trouble picturing green crabs using their claws to nip off eelgrass stems, mowing down hundreds of acres of inshore meadows all along the Maine coast, but that’s what they did.

Add warmer waters due to the accumulation of greenhouse gases in the atmosphere favoring green crab reproduction, and I quickly saw that given their appetites as individuals, a spike in their numbers could result in a loss of eelgrass throughout the state. Fishermen are now taking green crabs as bycatch, developing a new market for their use as fertilizer, catfood, and lobster bait.

The future, recently thought to be far ahead, is upon us. I have no notion how this drama will play-out due to changing conditions, but it is clear that tomorrow will differ from today in ways I never imagined.

This is the last example I will give of my firsthand engagements with nature. My next post will be a summary of what I have learned from my lifelong natural experience. Then I will move on to the cultural level of my engagements, which I see as engagements with nature once-removed. That is, with nature in human disguise.

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