Harbor Seals, Tidewater Glaciers and Climate Change

This post is dedicated to the late Dr. Vera Alexander, marine scientist, equestrian, musician, philanthropist and much more. It was WC’s privilege to serve as a marine technician on the R/V Acona in 1967 on a cruise where Dr. Alexander, a newly minted PhD, did some of the original research on the relationship between Harbor Seals and tidewater glaciers. Vera Alexander taught WC about the importance of curiosity in life and science, a lesson WC still cherishes today.

Harbor Seals hauled out on an iceberg, Meares Inlet, Alaska

If you’ve been on a ship in a glacial fjord, up near the snout of a tidewater glacier, you know that they seem to be as sterile as the moon. It’s not just the freezing cold air flowing down the glacier, or the barren rock walls framing the seawater. There’s no sign of life in the water, either.

Except for the harbor seals. In the right time of year and location, if there is glacial ice floating in the water there are usually harbor seals around, sometimes in amazing numbers. In 1967, WC worked under the supervision of Dr. Vera Alexander, the only woman scientist at the University of Alaska Institute of Marine Science, as Dr. Alexander tried to puzzle out why the seals were there, what they ate in an apparently near-sterile environment and how the species had adapted to such a hostile environment.

Meares Glacier snout; note the small dark dots just left of center

To answer questions, the R/V Acona ventured to College Fjord in west Prince William Sound, where we censused seals, tried to estimate ages and sex of the animals, monitored movement in and out of the fjords and studied the seawater characteristics. Using the depth finder as a fish finder, she tried to find out what fish species might be present at what distances from the glacier snouts. Using drogue nets, we sampled the invertebrates that were present.

Harbor Seals, face of Meares Glacier, Meares Inlet, Alaska

An unfortunate part of being a lowly deck technician is that you don’t get to see the analysis of the data, or the publications that may result. But it was immediately obvious that one of the reasons the Harbor Seals were where they were was to give birth. We saw afterbirths on many ice floes and icebergs, and young pups were everywhere. Females were nursing the pups. So it was a reasonable inference that the Harbor Seals were present to avoid predators as they birthed and raised pups. We saw Orcas at the seaward end of glacial fjords, but not up where the seals were. And by hauling out on icebergs, the Harbor Seals avoided land-based predators.

But what did they eat? Water at the snout of a tidewater glacier is laced with glacial flour, the very fine mud the glaciers grind of the bedrock on which they move. That results in very high nutrients in the water column, mixing of fresh and salt water and very high levels of plankton. The oxygen, phosphate and nitrogen levels in the mixing zones between the deeper salt water and the surface fresh water were so high the Dr. Alexander didn’t believe the test results at first, and made us run the tests multiple times.

High nutrient levels mean abundant plankton, which means abundant plankton-eating invertebrates and, in turn, fish that eat those invertebrates. And Harbor Seals to eat those fish. It only looks like a desert to surface-dwelling humans. The Harbor Seals are there because the icebergs are a safe place to pup, with abundant food and fewer predators.

In late summer and early fall, after the season’s pups are weaned, the seals use to icebergs as haul out while they molt, growing a fresh outer coat of fur for the coming winter. Like pupping, it’s a high energy process and the ready food makes it less stressful.

Harbor Seals, Bear Glacier, Resurrection Bay, Alaska

The week-long study started to answer the questions Dr. Alexander had asked. And, when WC’s colleague, David White, asked Dr. Alexander why she had decided to focus on Harbor Seals, she described a tourist trip from Valdez to Columbia Glacier with the then brand-new Stan Stephens Charters to see the glacier. She noticed the extraordinary number of Harbor Seals around the snout of that mammoth glacier and wondered why. There’s a lesson in power of curiosity if you needed one.

Like everything else on our poor planet, Harbor Seals are being impacted by anthropogenic climate change. Tidewater glaciers are vanishing. Columbia Glacier, where Dr. Alexander saw the Harbor Seals that raised her curiosity? It’s retreated 15 miles up the fjord, separating into an east branch and the main branch. The east branch is nearly aground, and won’t be a tidewater glacier much longer. The main branch continues to retreat. In College Fjord, where Dr. Alexander did her Harbor Seal research, and where the Harriman Alaska Expedition in 1899 identified a dozen or more tidewater glaciers, there are now just two glaciers that reach the sea. Even in Glacier Bay National Park, a place completely filled with glaciers when Captain George Vancouver happened by, there’s just one remaining tidewater glacier on the east side of the bay.

What does the loss of tidewater glaciers mean for Harbor Seals? Obviously, elsewhere in their North Pacific range the species breeds and molts just fine with shoreside haul outs. There are an estimated 35,000 Harbor Seals in California, and none of them have likely been on ice floes. But in a harsher climate the loss of the safer iceberg haul outs may be critical. We don’t know. But WC bets Dr. Alexander would be curious.

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