The Observer Effect

One universally accepted principle in the study of physics is the observer effect, which acknowledges that the very act of observation alters the phenomenon being observed. This fundamental law exists in the underwater world as well, and it is man himself who effects the change.

When you dive into the alien world of the ocean, your simplest actions — regardless of your intent — and your very presence, by the nature of your physical size, equipment, movements and sudden appearance, have an effect upon the environment’s natural inhabitants.

Like it or not, human presence in the ocean is intrusive. The life forms there face consequences from humans’ clumsiness or carelessness as well as from their purposeful actions. This not a judgment that requires the assignation of good, bad or neutral designations; it is a fact. Actions cause reactions. In addition to obvious activities such as tropical fish and shell collecting, spearfishing, underwater photography, and the feeding or attracting of particular species, human engagement with marine ecosystems brings about effects that are direct results of human presence.

A red pygmy seahorse is attached to red coral
Pygmy seahorse in Raja Ampat

These effects range from the relatively minor (disturbance or temporary displacement) to the more blatant (the interruption of feeding or mating) to the indefensible (harassment, injury or provocation of a creature’s fight-or-flight response). The most serious repercussions include fatal outcomes for sea life. Scuba divers who are caught up in the strange beauty and complexity of a reef environment may fail to ponder how the inhabitants of that reef react to their presence.

Blue Corner is arguably Palau’s signature dive; it’s a moderately shallow rock and coral plateau jutting out from an inshore fringing reef with a sheer drop-off into deep water. The site is renowned for excellent visibility and a strong current that runs parallel to the edge of the reef. It offers divers a chance to see schools of many different species of fish, such as chevron barracuda, trevally, snappers and others. Sea turtles and sharks cruise past in the blue, well within a diver’s field of vision. The dive site is a crowd-pleasing favorite, and the majority of divers surface delighted with the experience and absolutely unaware of any impact they may have had on the site.

Once back aboard the boat, there will be mention, perhaps even proud boasting, of seeing sharks “naturally” out in the blue, unlike at other dive locations where scent attractions are used to overcome sharks’ natural wariness. But upon closer inspection this is a delusion. If you were to dive Blue Corner without other divers you would discover an entirely different Blue Corner. The schools of shining, silver chevron barracuda that can just be seen in the distance during a high-traffic dive are usually on the reef flat itself, above the sand gullies and schooling between the coral heads. They’re not out in the blue, among their predators and away from fish they may prey upon. The same holds true for the schools of trevally and snappers. These are reef fish, which by definition are naturally inclined to stay on the reef. Even the sharks would be above the reef flat, cruising among the coral heads, patrolling their territory in search of unwary prey.

When a group of divers approaches a reef, moving along with strong and determined fin kicks, fish see the divers’ physical forms, and the silhouettes are unlike those of any other animal likely to be encountered in the sea. Divers are rather large — of a size generally associated with predators — and have what appear to be two tails moving up and down. Then there is the noise. Perhaps more than any other sound divers make, the gurgle and bubbling of air exhaled through regulators is incessant and very loud. This is especially true to animals with acute acoustic sensitivity — a common adaptation in a medium in which sound travels five times faster than in air. “The Silent World” is anything but silent when scuba divers enter the sea.

School of barracuda hunting for a snack
Barracuda school at Blue Corner, Palau

Compounding the loud noise is the related effect upon a fish’s “sixth sense”: its lateral line. The lateral line is a system of sensory organs that aids in predator–prey interaction, spatial awareness and orientation. It relays signals to the fish’s brain about objects in the vicinity as well as continuously monitoring the fish’s immediate surroundings, analogous in practice to a proximity alarm or whiskers in mammals.

With these senses combined, fish not only can see the physical form of an approaching diver and hear the noise of the equipment, but they also can watch as the bubbles emanating from a diver’s regulator float upward, expanding as they ascend and manifesting the signature form of a large inverted pyramid above the diver. In the sensory-processing centers of a fish brain, this stimulus is generally alarming enough to interrupt its routine and trigger its instinct to flee.

Somewhat tragic instances of diver displacement can occur with egg-laying fish, which are extremely active and expend a tremendous amount of energy to bring about the next generation. They carefully tend to their nests of thousands of embryos gestating within fragile, transparent eggs: They aerate the eggs to make certain that oxygen-rich water bathes them and to prevent the growth of algae; most important, they defend those nutrient-rich eggs against predators until the young hatch.

A titan triggerfish may well be able to defend its egg nest against a diver who inadvertently crosses into its protective zone. The diver is perceived as a large predator by the triggerfish, which is fearless and unrelenting in defense of its territory against the hapless diver. The triggerfish will swim to confront the diver at frenetic speed and perhaps bite a chunk out of him with its formidable teeth and strong jaws. However, while the triggerfish is on the offensive, opportunist egg-eaters such as wrasses, surgeonfish and butterflyfish will take advantage of the opening in defenses. They dart in to gorge upon the momentarily unprotected eggs in an unabashed frenzy, while the triggerfish deals with the intruding diver.

Buck-toothed titan triggerfish swims toward camera
Territorial females such as this titan triggerfish may guard their egg nests aggressively against all comers.

A similar outcome occurs when a diver strays too close to fish such as the sergeant major damselfish. They lay their nests of thousands of eggs upon rocks and protect them from neighboring generalist predators; but rather than confront a diver, the tiny damselfish flee in the interest of self-preservation, abdicating their protective roles as guardians. The opportunists instantly swarm, plundering gluttonously. In these situations, the future fish generations are affected by inadvertent intrusion.

Divers who are more observant and situationally aware — better able to read the reef and the behavior of its inhabitants — and conscious of their impact on those inhabitants can take measures to avoid interfering or at least minimize the effects of their presence.

Divers have been frequenting some sites for 30 years or more, and some animals have figured out how to use divers to their advantage. This is especially evident on night dives at some well-established sites in the Red Sea. As you swim along in the perfect blackness of the night with your torch illuminating finds here and there, a glance to the periphery of your light’s beam will reveal one or more lionfish, delighted to have a diver pointing out sleeping fish to be gobbled up. Alas, these situations have become unavoidable unless one wants to give up night diving entirely.

Some planned dives are unquestionably conscious decisions to enter situations that may disrupt animals’ lives. Visits to cleaning stations can be counted among these. Cleaning stations are particular spots on a reef that are home to various species of gregarious wrasses, whose niche on the reef is to feed upon external parasites on the bodies of manta rays and other large fish.

It’s easy enough to rationalize such excursions as not being too intrusive. With careful planning, decent instruction, a modicum of skills, good breathing technique and luck, divers may observe cleaning behavior — a fascinating symbiotic arrangement between enormous manta rays and tiny wrasses. Generally, if conducted in a small group of participants who minimize their silhouettes by trying to blend in with reef cover, staying low, keeping movement to a minimum, breathing slowly, leaving an open passage for the mantas to approach and depart, and allowing time for the manta rays to become used to the bubbles, the cleaning phenomenon can be observed. The normally wary manta rays may eventually overcome their predator-avoidance instincts and become accepting of the intruders’ presence to be relieved of parasites. But should another boatload of divers drop in on the cleaning station while the first group remains motionless and respectful of the animals’ comfort level — as happens all too frequently in the Maldives and Indonesia — then the mantas will bolt for the blue and keep a distance from the cleaning station.

Some might conjecture that the mantas could go to another cleaning station unknown to divers; that may be true, but it fails to consider the caloric needs of the wrasses that perform the cleaning service. If they cannot feed on the parasites brought to them by large manta ray hosts because divers keep the mantas away from those cleaning stations, do the wrasses eventually starve and die? As most fish are territorial, it seems unlikely that small wrasses forced to migrate from their cleaning station due to diver pressure would be welcomed by the wrasses established at another cleaning station.

Tiny red fish inside the mouth of a spotted fish
A fish-eat-fish world in Raja Ampat

When it comes to encountering cryptic critters, invasive intrusion is a given. Pygmy-seahorse fascination is a well-known scenario on dive boats. Speculations about whether constant intrusion, lights or photography has a detrimental effect upon the diminutive members of the seahorse family are legion. On any trip within the pygmy seahorse’s range, it is inevitable that a dive guide will indicate one using a pointer stick, a magnifying glass or his fingers to identify a quarter-inch seahorse hunkered down in the branches of a gorgonian sea fan. It is a rare situation when the guide, in the process of doing what is expected, does not touch the gorgonian to make the flowerlike polyps retract to improve the view of the seahorse. The effect of this intrusive custom on the pygmy seahorse is obvious, but the overlooked effect is that the polyps retract a lot more than they naturally would, and when the polyps retract the coral cannot feed. Furthermore, these human interactions may obliterate the protective slime that covers the sea fan, possibly weakening it and making it susceptible to disease.

Even snorkeling can have an observer effect, as I’m often reminded when exploring certain inshore reefs of the Red Sea. There is a shallow bay where tourists are taken daily on a dozen or more safari boats, each carrying as many as two dozen vacationers, to have a snorkel experience among the bay’s corals and fish and watch green sea turtles feeding on seagrasses in the shallows near the shore. It is not uncommon to see more than 100 people spread out across the bay at the same time. While they are told in briefings not to stand on or touch the corals or come in contact with the sea turtles, with so many people the exceptions occur daily, and the obvious transgressors behave appallingly. When the turtles are left alone, they feed on seagrass for long stretches of time, surface to breathe and continue all day long; when the turtles are disturbed, they move off with slow but deliberate speed.

Another unfortunate and not-infrequent situation in the region occurs when the area’s sole dugong is in the bay, also feeding upon seagrasses, and the general alarm is raised to the throng of tourists, who erupt in a cacophony of screams and shrieks. This dugong, known locally as Dyson, behaves uncharacteristically for a dugong, a species that’s generally elusive and retiring. Dyson is tolerant toward humans intruding in his feeding areas, yet even Dyson has his limits.

What starts off as a genuine desire to observe a relatively rare, large, charismatic and harmless aquatic mammal in its natural environment degenerates quickly into a mob scene straight out of a horror film. Rather than keeping a respectful distance and floating passively above the animal as it feeds rather obliviously 15 to 20 feet below, snorkelers kick their fins and paddle furiously, pushing past each other, kicking, elbowing, clawing and even climbing over one another to be directly above the animal or next to it when it has to surface for air.

Group of hammerhead sharks meet at a cleaning station
A cleaning station at Alcyone, Cocos Island

The dugong uproots and munches on seagrass stalks while spitting out billowing plumes of sand as it makes furrows in the soft seabed. A dugong’s strictly seagrass diet requires an inordinate amount of feeding, as seagrass is modest in nutrition. Thus, dugongs, like their terrestrial cousins the elephants, need to eat constantly to thrive.

When humans motivated by excitement or a lamentable need to show off begin dive-bombing the feeding dugong (or trying to touch or grab or ride it) and crowding it when it comes to the surface to breathe, its behavior changes. Dyson is not only harassed, he is actively pursued and disturbed to the point that he can no longer feed. The eventual outcome is that Dyson departs the bay, swimming away forcefully and leaving shouting, deluded humans high-fiving in its wake. These snorkelers pushed the act of observation into an act of harassment, and the result for the dugong is that he cannot feed where he needs to feed and must expend precious energy searching for food where he can feed on it in peace — or die trying.

The possibility of interacting with sea life is perhaps the most irresistible and addictive aspect of going into the sea, but we have to accept that every action we take in the sea will likely have consequences for the life there. This is an unavoidable aspect of submerging ourselves in a world of which we are not naturally a part. Each individual must decide what kind of impact he or she is prepared to live with.

Two manta rays meet at a cleaning station
A manta ray cleaning station in Raja Ampat

In many places, the animals most likely to interact with divers are marine mammals. This is not as common an occurrence as it might be because laws in many countries forbid humans from getting close to marine mammals, particularly whales and dolphins. But for those willing to travel to places where regulations are more lax, the rewards of marine-mammal interactions are great. In Mexico, the Galapagos Islands and South Australia, among other places, sea lions can be inquisitive and playful. Some sea lions will seek interaction with waterborne humans by gently biting a diver’s fins or wetsuit hood or by swimming dizzying loops and barrel rolls around a diver.

Humpback whale calf cavorting at the surface.
A humpback calf checks out the camera in Tonga

If one travels to one of the few places where swimming with whales and dolphins is permitted, then the opportunity for truly magical experiences is a distinct possibility. In the Kingdom of Tonga, for example, it is legal to swim with humpback whales when with a licensed operation and in the company of a licensed guide. Humpback whales migrate from Antarctica each year to mate and calve in the tropical waters of the South Pacific. The whale season is four months long, and during that time a newborn whale calf learns about the world around it as it grows an inch and 100 pounds each day on its mother’s rich milk, gaining strength for the long journey back to Antarctic waters at the season’s end. During this time each mother keeps watch over its baby but grants the young whale a bit of leeway to explore the new world. Calves can be inquisitive and will leave the protection of their mothers to investigate strange things, and to a newborn whale there are probably few things stranger than human beings snorkeling in rolling seas. As the snorkelers are clumsy, so too are the humpback calves just learning how to swim and dive and breach.

If one is lucky, while floating next to a 45-foot humpback whale mother with her calf tucked beneath the shadow of her body, her great eye will fixate upon your intent gaze across a few yards of open water, and you will instantly comprehend that you have made eye contact. A shudder, a tingle, a frisson may accompany the realization. There is no way of knowing what the whale is thinking, but there must be a glint of recognition — an acknowledgement of a kindred species. This recognition found in the eye of any animal connects us to the natural world from which we have become increasingly alienated. When a marine mammal initiates an interaction with a person, there is an effect — a cross-species connection — even if it lasts only moments.

When an animal with intelligence different from our own, living in a world so unlike ours, willingly overcomes its fight-or-flight instinct and draws in for a closer look at strange human animals in an aquatic environment in which they are ill-equipped to survive, then one thing is certain: The animal is the observer, and the effect they are having is on us.

© Alert Diver — Q4 Fall 2013