Ecosystem - a community of living organisms in conjunction with the non-living components of their environment (things like air, water and mineral soil), interacting as a system.
During a day on the water we might see a bald eagle swoop down from its perch high up on a pine tree or catch sight of an osprey diving in its characteristic ‘claws first’ fashion for a fish. Quite often we’ll watch seals eyeing us as we glide by and occasionally a porpoise will surface quite close to our kayaks. And since in a day we’re paddling past literally hundreds of lobster buoys, almost everyone has a question about lobsters – how often the traps are emptied, whether they are fished year round, what’s the word out there on climate change - is it affecting the lobster catch? We see clams, mussels and other shellfish in the intertidal zone on islands along with several species of marine algae. We camp on granite islands which are covered with a layer of acid soil just deep enough for a few species of shallow-rooted trees like pine and fir.
I’m often asked by kayaking clients to include more information on the website about the island environment of Deer Isle and Stonington. So here it is… a brief survey of some of the features of the island ecosystem that we experience here during the summer months.
There are almost fifty bird groups listed in the 'Quick Key to Birds of Deer Isle', a handy booklet written by Marnie Reed Crowell and Kenneth L Crowell and published by the Deer Isle Conservation Commission. There are just a few that we see regularly in the coastal zone in summer.
Twenty years ago it was unusual to see a bald eagle in the area. Now they’re quite commonplace and last year we sighted a bald eagle on about half of our trips. The bald eagle is unmistakable by virtue of its size. With a wingspan of up to six feet or more, to see an eagle swoop down from its perch from atop one of tallest trees, with its characteristic white head and broad dark wings, is breathtaking. I’ve had clients say that the trip was worth it just to see the eagle up close. (Bald eagles, by the way, are not bald - the name derives from an older meaning of the word ‘bald’ which is ‘white-headed’)
Eagles return to same nest each year, so it’s safe to say that on a particular island we’re seeing the same bird year after year. Along with illegal hunting, the pesticide DDT was a major contributor which led to their near-extinction in the 1950s. Interestingly, DDT is not lethal to bald eagles but DDT interferes with calcium metabolism which in the bald eagle’s case resulted in thinning of egg shells. During incubation in the nest, the eggs were quite literally unable to support the weight of the adult bird. The population plummeted until measures were introduced to eliminate the use of DDT and in the 1960s to declare the bald eagle an endangered species.
We’ve seen fewer ospreys in the region in the past couple of years – last year we didn’t see any. It is possible that this is because raptors like osprey and bald eagles compete for territory. Until recently it’s been considered unlikely that an eagle would attack an adult osprey. However, in 2016 there were number of camcorder videos released which showed bald eagles harassing parents and chicks in the nest. One of them, from Hog Island, just 50 miles from Deer Isle shows a bald eagle removing an osprey chick from the nest. (http://www.audubon.org/news/this-rare-video-bald-eagle-attacking-osprey-nest-incredible-display-speed-and. You’ll know an osprey when you see how it catches fish in its characteristic way - feet first in the water. Osprey are one of only two species of raptor (along with owls) where the outer toes are reversible allowing it to grasp a fish with two toes in front and two behind.
Cormorants are colonial birds, related to the pelican, and you’ll see groups of cormorants around Deer Isle and Stonington on rocks with their dark wings outstretched and drying in the sun. They are highly efficient diving birds, diving from the surface of the water rather than from the air like the raptors and using their wings underwater to propel themselves. They have a characteristic dive which gives them a streamlined entry into the water. Since they dive deep, they’ll disappear from view for what seems like minutes. They have short wings relative to their body weight, and they are are poor fliers.
We frequently see guillemots in small groups and in the spring it’s common to come across a pair together with their newly hatched chicks swimming behind them. They belong to the auk family (as do puffins) and are easily recognizable with their black coloration and white wing patches. If you see them out of the water, they’re also identifiable by their red legs and feet which are near to the rear of their bodies, like a puffin. They bob along in small groups in flat and choppy water, occasionally diving then resurfacing to rejoin the group. They have small wings and are not particularly graceful in flight. Their diving and swimming ability, however, is legendary – they’ve been videotaped diving to depths of over 500 feet as they ‘fly’ underwater looking for fish.
We hear loons more frequently than we see them since they are easily disturbed and like to keep their distance. They have an eerie, characteristically mournful call. Often, particularly late in the season we’ll see them up close on the water in the early morning. The loon has unmistakable markings, a black head with a cross-hatched gray body and a dark ring around its neck. If you are close enough you can see that their eyes are red or dark brown. They are the size of a large duck but is distinguishable from a duck in that they seem almost to be in the water rather than on it - the rear part of their body is submerged when swimming. Getting off the water into the air is difficult – you’ll see them running across the water flapping their wings trying to get airborne since their bodies are relatively heavy. Once in the air, however, they are tremendous fliers and have been recorded as flying more than 1000km in a day.
Gulls need no introduction. It’s no accident that they that they are found in such a wide range of habitats - not only on the coast. They are among the most generalist feeders of all birds, in the air they are wonderful fliers, on land they can walk and run efficiently, and in the water, they are expert divers and swimmers. They are colonial, nesting and feeding in groups. They are highly intelligent with a whole range of methods for finding and catching food. We often see them dropping shells of clams or mussels onto rocks to get at the shellfish inside. They’ll fly some distance to find a ‘good’ rock for breaking shells and there is even a learned component to this activity in that older gulls seem to be better at it than the young ones. The technique is unique to gulls. Gulls mate for life and they return to the same location each year for nesting.
Green Sea Urchin
I found this specimen minus its spines, bleached in the sun and washed up on a beach on Sellars Island, Brooklin . Almost everyone who sees a sea urchin will pick it up to examine it - their fivefold symmetry is irresistible! In life, sea urchins (Class Echinidea) are covered with moveable olive green spines and five rows of reddish purple tube feet which protrude through pores in the rounded shell or ´test´. If you find a live one and touch it, spines will move towards the point of touch.
Sea urchins have no visible eyes, legs or means of propulsion but can move over a hard surface using their tube feet in conjunction with their spines. For camouflage, tube feet hold bits of algae and shells agains the spines. The mouth has an efficient chewing structure with five triangular teeth for munching algae and attached animals. During low tide sea urchins retreat to crevasses under boulders and among kelps in the lower tide zone. Though the spines are fierce looking, sea urchins are eaten by lobsters and fish like herring and cod.
Sea urchins are a delicacy in many parts of the world, notably Japan. Beginning in the late 80s there was aggressive overharvesting in the Gulf of Maine for export which resulted in a 90% depletion of stocks - overharvesting resulted in a tipping point for the system, shifting from an urchin-dominated subtidal zone, to one devoid of sea urchins and teeming with crabs and lobsters that now thrive in established kelp forests. Efforts by the Maine Department of Marine Resources to come up with an effective management plan to bring back the sea urchin are ongoing.
The Blue Mussel is a bivalve molusc and is an unmistakable feature of the intertidal zone and found on all the islands around Stonington and Deer Isle. You´ll find their single shells scattered on beaches at low tide and you´ll see live mussels attached to rocks either singly or in clumps. If you look closely you´ll see the fine threads on their feet which allow them to attach and hold tightly onto rocks as the tide comes in and out. When the population is reduced in a particular area they tend to aggregate into clumps of individuals, attached to each other with these same fine threads, and it´s thought that clumping may increase reproductive success in low density populations. Immature mussels are preyed upon by a variety of other invertebrates. The adult is preyed upon by seagulls which you can see picking them off the rocks, flying thirty or so feet in the air and then dropping them onto rocks to crack their shells - it´s as though the seagulls know just how high to fly to do this with maximum effect.
Barnacles are crustaceans found only in salt water environments and are, as you’d expect, sessile, that is they don’t move around once they’re past the larval stage - they basically spend their adult lives lying on their backs. But surprisingly, they do have limbs - they just don’t use them for walking. The limbs are long and feathery and protrude upwards into the water and filter food such as plankton from the water, moving the plankton towards the central mouth. Barnacles also absorb oxygen through their limbs. And if that weren’t enough, there are photoreceptors on their limbs which let the barnacle know when there are changes in light intensity. These signals result in opening and closing of their central mouth.
Barnacles it seems are on every rock face in the upper tidal or ‘splash zone’ on the islands in this region, and you can see them at their most active when the tide is high and just about to ebb.
Starfish or sea stars are star-shaped echinoderms belonging to the class Asteroidea. I took this photo of these specimens (Lepasterias tenera), clinging to a barnacle-encrusted rock at low tide near Naskeag Point, Brooklin. At the lower surface of their arms, sea stars have tube feet with adhesive suckers at the tube feet tips which are arranged in grooves along the lower surface. Tube feet operate through hydraulic pressure and are used to pass food to the mouth at the center of the lower surface. Sea stars will eat bivalves like mussels as well as periwinkles, barnacles and pretty much anything which comes their way, hence the term ‘opportunisitic feeders’. Starfish are deceptively aggressive and will actually pull apart the two valves of a mussel shell enough to insert its stomach between the two halves. The sea star then proceeds to digest the barnacle's soft tissue. It is well known that sea stars can regenerate an arm or two if the arm is eaten by a fish or a lobster.
We see fronds of sugar kelp clinging to rocks in the lower tidal zone of many of islands when the tide is out. Sugar kelp is olive or golden in color and each frond has a stalk with a single blade and is anchored to its support by a branched holdfast. Fronds can grow to over 20 feet long though the ones we see are typically five to ten feet long. Their holdfasts will attach to ledges, stones, mussels, pilings, even ropes – forming dense beds where substrate is firm, to thin clumps on muddy surfaces. Sugar kelp can tolerate a range of salt concentration, so as well as in the subtidal zone, it is also found in brackish estuarine waters and tidepools. Sugar kelp is a edible and is rich in iodine, protein, calcium and vitamin C and can be eaten raw or added to rice, soups or stews, etc.
Between low and high tide just below the barnacle belt and above the Irish Moss and Kelp zones is found the Rockweed Zone. Rockweed is a brown algae and is made up of twisted blades and rounded bulbs or receptacles which have ridges on two sides .Rockweed is rich in a wide range of minerals, vitamins, and a host of bioactive compounds including fucoidan, a complex sugar that has a variety of medicinal applications. Rockweed is often powdered and sold to make green drinks, teas and is taken as a medicinal supplement. Rockweed is often found on beaches as a 'stranded seaweed', attached by its holdfast to a small rock which has become dislodged by the tide. Our dog Pippa has a favorite game of tearing the seaweed off its small piece of rock after the tide has gone out.
THE geological ENVIRONMENT
Granite - the dominant bedrock
The dominant bedrock type is granite which has a characteristically pink color and which has been used in the construction of several major structures in cities such as New York - for example, sections of the Brooklyn Bridge and also the New York Municipal Building are made of Deer Isle Granite. Deer Isle granite is quite unusual and is made up of large rounded pink crystals (orthoclase) which are typically surrounded with a white rim of plagioclase. This type of granite is called Rapakivi granite which is a Finnish word which describes its texture - it means ‘crumbly’. So though granite itself is hard, you’ll often see jagged pieces broken off bedrock as well as stones which have been rounded principally by water and ice erosion.
evidence for Glacial activity
The rocks of the islands were formed millions of years ago and what we see on the shoreline is a combination of this very old bedrock and the rubble - rounded stones of various shapes and sizes – which were left behind from retreating glaciers. You’ll see rounded glacial erratics of granite, sometimes 12, 15 or even 20 feet in circumference which were dragged to their current position, 10,000 or more years ago at the time of the last northerly retreat of glacial ice. These boulders would have been carried considerable distances at the base of the glacier and scraped repeatedly on bedrock and by smaller stones. Some of the best examples of these erratics that I’ve seen are on Hog Island in Brooklin, this one is more than 30 feet in height.
Changes in Sea Level