Are Galapagos Expedition ships a source of water pollution?

We regularly come across concerns about whether expedition ships in Galapagos may be a source of water pollution.  We go over the issue in this short article.   

What waste? 

Ships do not throw inorganic rubbish into the sea.  It is collected and disposed of when the ship returns to port at least once a week – joining the rubbish produced in towns and sent to a landfill once any recyclable materials are taken care of.  Ships don’t dump oil or fuel into the sea either – they have no interest in doing so.  Fuel is used to power the engines, and exhaust, like for all internal combustion engines, is released into the air.   Organic kitchen scraps are allowed to be disposed into the sea (at least 2km from shore), but only after having been chopped up. Such scraps quickly decompose and are the source of nutrients for marine organisms.  We focus on human wasted in this article.

It’s true that ships release human waste into the ocean as they navigate throughout the archipelago.  Whatever is flushed down the toilet (and almost all ships ask you to flush nothing but human waste down the toilet, providing a covered waste basked next to it for the paper) does end up in the sea.  Regulations require that wastewater pass through a type of industrial blender (primary treatment), turning it into more of a sludgy liquid before being released.

Is human waste a pollution concern?  We look at it in two ways:

  • Waste composition: Are the actual components of human waste harmful to the Galapagos marine environment?
  • Waste volume: Is the total amount of human waste released into the sea a concern?

Does the nature of human waste harm Galapagos?

Human waste is pretty much the same as waste generated by other animals such as fish, sea lions, whales and blue-footed boobies.  It’s a mix of organic matter, bacteria, high in nitrogen, fat and other organic compounds and elements.  There may be varying concentrations of different compounds between species, but at the end of the day, it’s the same kind of thing.  

Is this waste bad for the marine environment?

Biologists understand that animal waste is a rich source of nutrients.  Farmers spread manure on their fields to enrich them – and many of us do the same in our back-yard gardens.  Typically, if amounts do not exceed certain levels, animal waste is considered as a very valuable input into marine ecosystems, bringing in highly prized nutrients in waters that are generally nutrient poor.  Plankton thrives when nutrients are available - and in turn, the plankton forms the basis of a rich food chain leading right back up to whales, sea lions and sharks.   In this regard, one can conclude that human waste, by its composition, is actually beneficial to the Galapagos marine environment, like fertilizer is beneficial to a garden. 

However, it’s possible to overload an ecosystem with nutrients.  Doing so leads to eutrophication – a condition that occurs when an excess of nutrients leads to runaway algal growth. Algae proliferates, dies and is consumed by bacteria, which use up all the oxygen, turning such waters into dead zones for animals.  Eutrophication usually occurs in enclosed waters (lakes, slow moving rivers, estuaries or inlets) and rarely in the kinds of open waters one finds in Galapagos.  Still, there’s no harm in looking at the volume and concentration of human waste being released into the sea as a possible indicator of negative impacts.

Does the volume and/or concentration of human waste harm Galapagos marine ecosystems?

The best way to answer this question is to get a sense of the relative importance of human waste vs Galapagos wildlife waste that is released into the waters.   The Galapagos marine reserve is home to dozens of species that are larger than humans.  The weight of a single adult blue whale (up to 300,000 pounds, or 136,000kg), for example, is about the same as the total weight of all humans aboard expedition ships on any given day[1].  Arguably, the daily waste a blue whale generates must be in the same order of magnitude as the daily waste generated by all those people.  Don’t forget – when a blue whale has a bowel movement, it all happens in one spot, while human waste is dispersed over a vast expanse of ocean.  Yet eutrophication of Galapagos waters has never been a concern – it doesn’t happen because the relative amount of nutrients remains very much below the threshold that could lead to eutrophication. 

A whale of a bowel movement...


Getting back to that blue whale – it shows how just one individual of one species can produce as much waste as all the humans on board expedition ships – that alone should make it clear that human waste is a minuscule part of all the animal waste released into the Galapagos marine reserve every day.   If we just look at whales – the fact that over a dozen species of larger whales make Galapagos waters their home and they number in the thousands further illustrates the inconsequential nature of contributions made by humans.

But let’s keep on considering other sources of animal waste.

Occasionally seen in superpods containing 1,000 or more individuals, dolphins are very common in the islands.  It’s not unreasonable to conclude that tens of thousands of them spend a lot of time in the Galapagos marine reserve – and each one weighs on average over twice as much as a human.   You’ll also notice many sea lions while exploring Galapagos.   Their population has been estimated at about 50,000 – and each one is close to the size of an average human.   We’ve not even mentioned the millions of fish in the sea around Galapagos. From the tens of thousands of larger sharks, rays, tuna, to the ubiquitous smaller fish. And then there are all those seabirds.

Each one of these animals releases waste into the water.  It’s easy to conclude that the proportion of animal waste released into Galapagos waters that can be attributed to humans on expedition ships is infinitesimally small and that its incremental effect on the environment is literally no more than the proverbial drop in the ocean.   

A non-issue at sea, but not near towns

It’s clear that human waste released by people aboard expedition ships has no negative effect on Galapagos marine ecosystems.

However, there are waters in Galapagos that are demonstrably negatively affected by human waste.  These are found in the bays around which the main human settlements are built and where we find hotels, restaurants and more.  This is particularly the case in Puerto Ayora.  Here, approximately 15,000 people live around Academy Bay – and the town has no sewage system.  Used waters are flushed (in a best case scenario) into little more than holes dug into porous volcanic rock.  They easily flow into the bay.  Studies have shown the the levels of faecal coliform bacteria in the near shore at Academy Bay, along with other indicators of leaching sewage, are high enough to pose a risk to human and ecosystem health[2].  There has been talk about developing a functioning sewage treatment system in Galapagos for decades - but little has been done to date.  

So, rest assured, your time aboard your expedition ship is not contributing to the contamination of pristine Galapagos waters. 


[1] 65 ships, with an average capacity of about 25 guests, a 1:2 ratio of crew to guests and an average occupancy rate of about 75% means that, on any given day in Galapagos, there are a little over 1,800 guest and crew members on Galapagos expedition ships.

[2] Mateus, C.; Guerrero, C.A.; Quezada, G.; Lara, D.; Ochoa-Herrera, V. An Integrated Approach for Evaluating Water Quality between 2007–2015 in Santa Cruz Island in the Galapagos Archipelago. Water 201911, 937.

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