Welcome to the April issue of SEVENSEAS. This month, we travel to Tenerife, where Europe’s first Whale Heritage Site opens a deeper look at the Atlantic’s most contested marine corridors, the threats facing the Teno-Rasca sanctuary, and the pilot whale communities whose futures hang in the balance; a seven-day itinerary and a practical guide to the island’s water quality crisis round out the coverage. From Trinidad, Katrina Khan-Roberts explores how a mermaid named Mertrina can reconnect island communities with the sea. In Ghana, West Africa’s first diving bootcamp is training a new generation of coral guards. Dr. Narissa Bax explains how Antarctic blue carbon is reshaping the climate conversation, while a URI study questions the long-term promise of marine carbon removal. On the high seas, the shadow fleet of aging tankers has crossed into geopolitical flashpoint. You’ll also find coverage of UNESCO’s Cryospheric Sciences decade, the Seaworthy Collective’s latest BlueTech cohort, and coral restoration in Accra.

Tenerife’s Whale Sanctuary and Why Teno-Rasca Matters

Europe’s first Whale Heritage Site hosts 28 cetacean species year-round, but wastewater failures, coastal development, and a contested port project now threaten the Atlantic’s most protected marine corridor. [Read more]

A Nature Traveller’s Guide to Tenerife, Seven Days Deep

Beyond the resort strip: ancient laurel forests, volcanic calderas, cave villages, and dragon trees across a seven-day itinerary through one of Europe’s most ecologically varied islands. [Read more]

Is the Water Safe? Tenerife Beach Quality in 2026

EU legal action, criminal charges, and an 81 million euro cleanup plan follow years of wastewater failures across the island. A practical guide to where swimming is safe and where caution is warranted. [Read more]

What Tenerife’s Fish Are Telling Us About Ocean Health

Four hundred fish species, resident pilot whales, and migrating bluefin tuna share waters where reef habitats and seagrass meadows are declining. The signals from the sea are mixed, and worth reading closely. [Read more]

Tenerife: Into the Habitat of Pilot Whales, Seen Up Close

Resident pilot whale pods thrive year-round in Tenerife’s deep underwater canyons, their matriarchal societies holding knowledge passed across generations. A reflection on coexistence, awareness, and what the sea asks of us. [Read more]

Small Islands and the Currents of Change in the Caribbean

From a childhood watching Trinidad’s shoreline transform to creating Mertrina the mermaid, Katrina Khan-Roberts explores how storytelling and imagination can reconnect island communities with the sea. [Read more]

How Ghana Is Training the Next Generation of Coral Guards

In Accra, two conservationists founded Coral Reefstoration Ghana and launched The Dive Lab, West Africa’s first diving and underwater media bootcamp for marine biology students. [Read more]

Carbon and Nutrient Cycles Overlooked in Marine CDR Plans

A URI study reveals that carbon and phosphorus cycle through the ocean on different timescales, creating a “productivity hangover” that may cause marine carbon removal strategies to overestimate their long-term impact. [Read more]

Celebrating World Glaciers and Water Days Through Art

UNESCO launched the Decade of Action for Cryospheric Sciences in Paris, while five side events across the U.S. connected glacier research, maritime heritage, and artistic expression at museums from Maryland to New York. [Read more]

Antarctica’s Hidden Carbon Sink and the Science of Blue

Polar marine ecologist Dr. Narissa Bax explains how phytoplankton and deep-sea organisms in the Southern Ocean are reshaping the climate conversation around Antarctic blue carbon. [Read more]

The Shadow Fleet: From Environmental Threat to Flashpoint

Over 340 aging tankers now operate outside international safety standards, as military seizures, naval escorts, and flag-switching transform a maritime environmental crisis into a contest between world powers. [Read more]

Seaworthy Collective Launches Its Seventh Startup Cohort

Seven new BlueTech startups join the NOAA-backed Continuum program, building AI and data-driven solutions for ocean mapping, water quality monitoring, fisheries health, and the growing blue economy. [Read more]

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The question visitors to Tenerife are increasingly asking before they book is one that would have seemed unusual a few years ago: is the water actually safe to swim in? It is a fair and important question, and one that deserves a straightforward, evidence-based answer rather than either alarming exaggeration or reassuring dismissal. The situation is genuinely complicated, varies significantly by location and season, and is in the middle of a politically charged response from local and national authorities.

The Scale of the Pollution Problem

The water quality crisis affecting parts of Tenerife is not a tabloid invention. In late 2025, the Court of Justice of the European Union formally condemned Spain for failing to comply with the EU’s Urban Wastewater Treatment Directive, identifying at least 12 specific locations on Tenerife where sewage collection, treatment, and discharge into coastal waters was either inadequate or entirely absent. [1] This followed years of documented failures. Environmental analysis cited by campaigners estimated that approximately 57 million litres of wastewater are discharged into Canary Islands seas every day, equivalent in volume to around 17 Olympic swimming pools. [2]

The consequences became impossible to ignore in 2024 and 2025. Playa Jardín, a well-known black-sand beach in Puerto de la Cruz on the island’s north coast, was closed for almost a year after E. coli levels in the water significantly exceeded safe limits. Investigations revealed fractured discharge pipes, pumping stations operating without legal authorisation, and a wastewater treatment plant that had gone years without the mandatory inspections and repairs. [3] In August 2025, the Public Prosecutor’s Office took the unusual step of charging six officials — including a former mayor of Puerto de la Cruz and the island’s former Tourism Department head — with environmental negligence and mismanagement of public infrastructure. [3]

The Spanish environmental NGO Ecologistas en Acción, which publishes an annual “Black Flag” report ranking the worst-managed coastal zones in Spain, awarded black flags to both Playa Jardín and Puertito de Adeje in its 2025 edition. [4] Puertito de Adeje, on the island’s southwest coast, was flagged not for E. coli but for what the organisation described as poor management in relation to new luxury coastal development and an underwater garden project that critics argue threatens endangered marine species. [4]

Storm events have made the underlying infrastructure problems dramatically visible. When Storm Claudia brought heavy rainfall in November 2025, drainage systems in Garachico and Las Américas were overwhelmed, sending wet wipes, oils, and other debris onto the shore. Beachgoers in Las Américas reported finding white, greasy masses on the sand, which chemists explained as the product of soaps and oils in wastewater reacting when pushed out to sea. [5] The Canary Islands government’s own discharge register, updated in 2025, recorded 403 coastal discharge points across the archipelago, with more than half operating without full authorisation. [1]

The Response: €81 Million and a 2030 Target

In February 2026, Tenerife’s Island Council formally presented an €81 million infrastructure plan designed to address these failures over a four-year period running through 2030. The plan covers modernising outdated wastewater networks, increasing treatment capacity, preventing unauthorised coastal discharges, and improving coordination between the island’s municipalities, which have historically operated fragmented and sometimes incompatible sanitation systems. [6] Vice President Lope Afonso framed the initiative around a “zero waste” ambition and called on all local municipalities to participate in the 2027-2030 Cooperation Plan. [6]

The plan has been welcomed cautiously by environmental groups. The Tenerife Association of Friends of Nature (ATAN), which was among the first organisations to raise public alarms about the contamination crisis in early 2026, has called for more transparency about the actual scale of coastal pollution and demanded that tourists be given honest information about water quality at specific beaches rather than generic reassurances. [1] This tension between the island’s economic dependence on tourism and the imperative to communicate environmental problems honestly is not going away quickly.

Where Is It Actually Safe to Swim?

The water quality situation varies significantly across Tenerife’s coastline, and not all beaches are affected equally. The problems documented in official reports are concentrated primarily in the north of the island, around Puerto de la Cruz and parts of the northeast coast, and in specific southern locations where infrastructure has struggled to keep pace with resort development.

The southern resort strip between Los Cristianos and Costa Adeje generally maintains higher water quality, supported by more recently built sanitation infrastructure and EU Blue Flag certification at several beaches. Blue Flag status, awarded annually by the Foundation for Environmental Education, requires compliance with strict water quality testing, environmental management standards, and safety requirements — making it the most reliable indicator of consistently clean swimming water available to visitors. [7]

Practical guidance for 2026 visitors: check the current flag status at your specific beach on arrival, not the status from a previous season. Red flag means swimming is forbidden, regardless of the reason. Avoid swimming within 48 hours of heavy rainfall anywhere on the island, as storm runoff affects even beaches that are generally well managed. The north coast, including the Puerto de la Cruz area, carries higher current risk than the southwest. Beaches within the southern resort area with active Blue Flag certification — including Playa de Troya, Playa del Duque, and Las Vistas in Los Cristianos — are your safest options while the infrastructure improvements work their way through the system.

Looking Ahead

Tenerife’s coastal pollution crisis is real, but it is being taken seriously in a way it was not a few years ago. EU legal pressure, criminal charges against officials, a significant funding commitment, and genuine civic pressure from environmental organisations have combined to produce a political response with specific targets and timelines. Whether that response is adequate, and whether it moves fast enough to protect both public health and the island’s reputation, is a question that will be answered in the coming years.

What is certain is that the era of uncritical optimism about Tenerife’s beach water quality is over. Visitors deserve accurate information, and the island’s long-term interests as a destination are better served by honest communication than by silence.

Sources

1. BritBrief: Health alert for Canary Islands — tourists warned about beach water pollution, britbrief.co.uk, January 2026
2. National World: Warning to avoid 48 Black Flag beaches in Spain, nationalworld.com, June 2024
3. DaNews.eu: Prosecutor charges six officials over pollution at Playa Jardín in Tenerife, August 2025
4. Travel Tomorrow: Tenerife set to invest €81 million to clean up island’s coastline and reputation, traveltomorrow.com, February 2026
5. Canarian Weekly: Waste and pollution wash up on Tenerife’s coastline again, canarianweekly.com
6. Travel and Tour World: Tenerife Plans to Invest Eighty Million Euros in Overhauling Water and Sanitation Infrastructure, travelandtourworld.com, February 2026
7. Curious Expeditions: Is the sea clean in Tenerife?, curiousexpeditions.org, March 2026

Tenerife sits in the eastern Atlantic like a crossroads. Positioned roughly 300 kilometres off the northwest coast of Africa, the island intersects the paths of the Canary Current, warm subtropical surface waters, and the deep cold upwellings of the Atlantic basin. The result is one of the most ecologically productive marine environments in the northern hemisphere, a place where bluefin tuna from the Mediterranean share waters with tropical reef species and migratory whales from the polar ocean. What lives in these waters, and how those populations are changing, tells us something important about the health of the broader Atlantic system.

The Anatomy of an Exceptional Marine Environment

The waters around Tenerife support approximately 400 species of fish, a number that reflects the unusual convergence of marine provinces that the island straddles. [1] Its seafloor topography is dramatic: the island drops away steeply from the coast, reaching oceanic depths within just a few kilometres of shore. This proximity of shallow coastal habitat to very deep water creates conditions that support both reef-associated species and the large pelagic predators of the open ocean, sometimes within sight of the same beach.

In the deeper offshore waters, the Canary Islands are internationally recognised as one of the finest big game fishing destinations in the world, and for good reason. Atlantic bluefin tuna (Thunnus thynnus) pass through in their thousands between December and April, migrating northward toward Mediterranean spawning grounds. These are not small fish. Individuals regularly exceed 250 kilograms, and the largest bluefin recorded in these waters approach 450 kilograms. [2] Their spring passage coincides with dense schools of Atlantic mackerel (Scomber scombrus) and smaller baitfish that concentrate near the island, drawing the giants in from the open Atlantic.

Blue marlin (Makaira nigricans) and white marlin (Kajikia albida) are present from spring through autumn, the two billfish species that define Tenerife’s reputation among dedicated sport anglers. Spearfish (Tetrapturus belone) inhabit the deeper offshore trenches. Yellowfin tuna (Thunnus albacares), bigeye tuna (Thunnus obesus), wahoo (Acanthocybium solandri), and mahi-mahi (Coryphaena hippurus) complete a pelagic assemblage that few locations outside the tropics can match. [2]

Closer to shore, the volcanic reef structures support a different community. Atlantic amberjack (Seriola dumerili), barracuda (Sphyraena viridensis), grouper (Epinephelus spp.), and European sea bass (Dicentrarchus labrax) inhabit the rocky substrates, alongside numerous wrasse species, bream, and moray eels. The deeper sandy bottoms, where slow-jigging techniques are most effective, hold species less visible to tourists but central to local gastronomy: red porgy (Pagrus pagrus), sargo (Diplodus sargus), and various sparids that have been fished by Canarian communities for centuries. [3]

Reading the Signals: What Is Changing

The richness of this marine environment is not static, and the signals coming from the water are mixed. On one hand, the resident cetacean populations tell a story of relative stability. Whale Watch Tenerife, which has logged cetacean sightings systematically since 2018, recorded 17 different species in both 2018 and 2023, with short-finned pilot whales (Globicephala macrorhynchus) and bottlenose dolphins (Tursiops truncatus) present on nearly every survey day. [4] In 2025, orca sightings and encounters with fin whales were notable additions to the year’s record. [4] The continued presence of these apex predators is generally a positive indicator of ecosystem function.

On the other hand, the EU-funded OCEAN CITIZEN restoration project documented concerning trends at the base of the food web when it began its work on the island in 2024. Fish populations associated with rocky reef habitats have declined significantly compared to historical baselines. Seagrass meadows (Cymodocea nodosa), which serve as nurseries for juvenile fish and feeding grounds for sea turtles, have retreated across multiple coastal areas due to sedimentation, pollution, and rising water temperatures. Rocky reefs have been degraded by a combination of physical disturbance and the effects of ocean acidification. [5] These are not peripheral problems. Reef habitats and seagrass meadows are foundational to the productivity that ultimately supports the entire marine food web, from the smallest reef fish to the bluefin tuna and the pilot whales that hunt above them.

The Atlantic regulatory framework governing commercial fishing has also evolved. EU fisheries ministers, meeting in December 2025, set 2026 catch limits with 81 percent of total allowable catches in the northeast Atlantic at maximum sustainable yield levels — an improvement on previous years, though the failure to agree a mackerel quota for 2026 due to disputes with non-EU countries was a notable setback. [6] For sport and recreational fishing around Tenerife, a growing culture of catch and release has taken hold among charter operators, particularly for bluefin tuna, billfish, and other large pelagic species. Most reputable charters now apply mandatory release for bluefin tuna, reflecting both changing regulation and a shift in the values of visiting anglers. [3]

What the Fish Are Actually Telling Us

Marine ecosystems are exceptionally good at communicating ecological stress, if we know how to listen. The presence of 28 cetacean species, including year-round resident pilot whales, tells us that the deep-water food web west of Tenerife remains productive. The decline of reef fish populations and seagrass cover tells us that the shallower coastal zone is under sustained pressure from human activity. The continued migration of bluefin tuna past the island tells us that large-scale Atlantic management is beginning to take effect after decades of overfishing. The appearance of orcas and large baleen whales in 2025 tells us that the waters retain the biological richness to attract ocean wanderers from across the hemisphere.

Tenerife’s marine environment is neither pristine nor beyond recovery. It occupies a contested middle ground where genuinely exceptional natural heritage coexists with the pressures of one of Europe’s busiest tourist destinations. Paying attention to what lives here, in all its scientific specificity, is the first step toward deciding what kind of relationship the island will have with its sea.

Sources

1. Wikipedia: Tenerife — fauna and marine ecology
2. FishingBooker: Tenerife Fishing — The Complete Guide for 2026, fishingbooker.com, January 2026
3. FishingBooker: Canary Islands Fishing — The Complete Guide for 2026, fishingbooker.com
4. Whale Watch Tenerife: Tenerife Whale Watching Season — cetacean sighting data 2023-2025, whalewatchtenerife.org
5. OceanCitizen EU: Reclaiming Tenerife’s Ocean, oceancitizen.eu, September 2024
6. European Commission Oceans and Fisheries: Fisheries ministers agree fishing opportunities for 2026, December 2025, oceans-and-fisheries.ec.europa.eu