What leaves the plantreaches the reef.

OceanBlu is building software for near-ocean wastewater plants, with an initial focus on coral reefs. We combine a plant’s own records and requirements with satellite, weather, and ocean data to suggest proactive management steps that keep the water and the environment healthy.

Talk to us about a pilotHow it works

Scroll to follow treated water from the outfall to a reef 2 km away.

In the plume50 m from the outfall

Treated wastewater has low salinity, so it is lighter than seawater and rises. When the pipe is offshore, the plume then spreads sideways with the current. Many small plants discharge at the shoreline or into a creek. Either way, the plume often hugs the coast, where corals live.

  • Nutrients

    Nitrogen and phosphorus feed seaweeds, which crowd out corals, and floating algae, which shade them. The chemical form of the nitrogen also matters. In a field experiment in French Polynesia and in lab studies, corals given extra nitrate bleached more often and for longer during heat stress, and more of them died. Lab studies also found that corals given ample nitrogen but too little phosphate bleached more easily.

  • Fine sediment

    Fine particles cloud the water and cut the light reaching the algae that live inside corals and feed them. The coarser grains settle out first, close to the pipe.

  • Chemicals

    Treated wastewater is often more acidic (lower in pH) than seawater. Near the outfall, before it mixes in, that can make it harder for corals to build their skeletons. It can also carry leftover chlorine (at plants that disinfect with it), metals such as copper, and traces of medicines and sunscreen chemicals.

  • Organic matter and bacteria

    As organic matter breaks down, it uses up oxygen in the water. In aquarium experiments, a strain of the bacterium Serratia marcescens taken from human wastewater caused white pox disease in Caribbean elkhorn coral.

What the plant cannot see500 m from the outfall

Many reefs lie off coasts where wastewater is only partly treated: by open settling ponds, or small plants with tight budgets, unreliable power, and few lab staff.

A plant knows what happens inside its fence, at least on paper. Past the fence, it usually knows very little.

OceanBlu combines satellite data, current modeling, and scientific knowledge of local ecosystems with the plant’s own data, and provides a detailed dashboard and suggestions that support both people and the environment.

Map of a small coastal treatment plant on the shore. A pipe carries its treated water about 1 kilometer offshore to an outfall. From there the discharge plume drifts with the current and widens, reaching a coral reef about 2 kilometers down-current. PlantOutfallPipeDischarge plumecarried by the currentReefN1 km
A small coastal plant, its outfall, and a reef 2 km down-current, drawn to scale.

How OceanBlu works1 km from the outfall

  1. 1. Start with the plant’s records.

    OceanBlu works from the records a plant already keeps: spreadsheets, PDFs, and handwritten bench sheets, gaps and all.

  2. 2. Add ocean and weather data.

    It adds reef heat stress, satellite images of water color, currents (estimated from tides, wind, and ocean models), rainfall forecasts, and any local monitoring. OceanBlu integrates these data sources and shows how confident each estimate is.

  3. 3. Suggest steps.

    Combined, these data are then passed through a scientific filter for the environment and biodiversity in your area. OceanBlu explains the risk in plain English or Spanish and suggests steps that suit the plant’s equipment and staff, to proactively optimize for outcomes. Nothing changes until an operator approves it.

  4. 4. Keep the record.

    OceanBlu keeps compliance summaries and a record of what was known when each decision was made. Every number links back to its source.

Plant flow and lab results (square = test missed)RainReef heat stress built up over weeksCurrent changes direction dynamicallySatellite murkiness and algaeCombined risk to the reefNOAA bleaching alert level 1Recommendation draftedDay 1Day 14
An illustrated two weeks. The curves follow the shape of real signals but are not data from any plant. Shaded hours are when currents run toward a heat-stressed reef while the plant handles extra flow. The same discharge carries different risk on different days.
  • Murkiness (turbidity)
  • Algae (chlorophyll)
  • Higher-risk hours

On the reef2 km from the outfall

A plume thins as it travels, but some of what it carries still reaches the reef, and that has measurable impacts.

But smart management helps. In a three-year field experiment in the Florida Keys, reef plots given extra nitrogen and phosphorus had twice as much coral disease, and one group of corals bleached three and a half times as often. Ten months after the extra nutrients stopped, the plots were no different from untouched reef.

The pink crusts are coralline algae. They give off cues that help young corals choose where to settle. In experiments, these algae were among the reef builders most sensitive to acidification, one more reason to make plumes less acidic near outfalls. Click or tap a pink crust to watch one settle.

Talk to us

We are looking for coastal utilities to pilot OceanBlu, and for funders and research partners to help build it. We would like to hear from you.

What a pilot involves

You share
The records you already keep: flows, lab results, and maintenance logs, in any format.
You get
A daily outlook of higher-risk hours for your reef, suggested steps, and draft compliance summaries.
Optional
A low-cost current meter near the outfall to sharpen the estimates.

OceanBlu is at an early stage: we are building the first version and looking for pilot partners.

Talk to us about a pilot

or write to hello@oceanblu.org

Who we are

  • Graham Patterson

    Co-founder of OceanBlu, and founder and executive director of REEF Scuba. Marine scientist with master’s degrees in marine biological resources (IMBRSea) and public policy. Experience in policy and program management, media and communications, and strategic partnerships.

  • Manuja Promodya

    Co-founder of OceanBlu. Deep-sea ecologist and an Erasmus scholar in marine biological resources (IMBRSea). ECOP Research Lead, Sri Lanka. Experience in coral taxonomy, ecology, and sustainable waste management.

  • Dilan Perales Garcia

    Programming and statistical analysis. Data-driven research and marine innovation, with a passion for ocean conservation.

Notes and sources

We keep the claims on this page conservative. Where the evidence comes from one site, one species, or the lab, the text says so or stays general. The two-week figure is an illustration, not data.

Reefs, heat stress, and sewage

  • Hughes and others, 2018. Spatial and temporal patterns of mass bleaching of corals in the Anthropocene. Science 359 (on heat stress becoming more frequent). Source
  • Wear and Vega Thurber, 2015. Sewage pollution: mitigation is key for coral reef stewardship. Annals of the New York Academy of Sciences 1355. Source
  • Tuholske and others, 2021. Mapping global inputs and impacts from human sewage in coastal ecosystems. PLOS ONE 16. Source
  • Brodie, Johnson, Waterhouse and Erdmann, 2019. Wastewater pollution and coral reefs: supporting science. C2O for UNEP. Source
  • Jones and others, 2021. Country-level and gridded estimates of wastewater production, collection, treatment and reuse. Earth System Science Data 13. Source

Nutrients: amount, form, and ratio

  • Burkepile and others, 2020. Nitrogen identity drives differential impacts of nutrients on coral bleaching and mortality. Ecosystems 23. Source
  • Wiedenmann and others, 2013. Nutrient enrichment can increase the susceptibility of reef corals to bleaching. Nature Climate Change 3. Source
  • Fernandes de Barros Marangoni and others, 2020. Unravelling the different causes of nitrate and ammonium effects on coral bleaching. Scientific Reports 10. Source

Chemistry and bacteria

  • US EPA, 1985. Ambient water quality criteria for chlorine (saltwater criteria as chlorine-produced oxidants). Source
  • Reichelt-Brushett and Harrison, 2005. The effect of selected trace metals on the fertilization success of several scleractinian coral species. Coral Reefs 24. Source
  • Downs and others, 2016. Toxicopathological effects of the sunscreen UV filter, oxybenzone (benzophenone-3), on coral planulae and cultured primary cells and its environmental contamination in Hawaii and the U.S. Virgin Islands. Archives of Environmental Contamination and Toxicology 70. Source
  • National Academies of Sciences, Engineering, and Medicine, 2022. Review of fate, exposure, and effects of sunscreens in aquatic environments (finds the field evidence still limited). Source
  • Sutherland and others, 2010. Human sewage identified as likely source of white pox disease of the threatened Caribbean elkhorn coral. Environmental Microbiology 12. Source
  • Sutherland and others, 2011. Human pathogen shown to cause disease in the threatened elkhorn coral Acropora palmata. PLOS ONE 6. Source

Coralline algae

  • Heyward and Negri, 1999. Natural inducers for coral larval metamorphosis. Coral Reefs 18. Source
  • Kuffner and others, 2008. Decreased abundance of crustose coralline algae due to ocean acidification. Nature Geoscience 1. Source

Recovery when the load drops

  • Vega Thurber and others, 2014. Chronic nutrient enrichment increases prevalence and severity of coral disease and bleaching. Global Change Biology 20 (the Florida Keys experiment, 2009 to 2012). Source
  • Bahr, Jokiel and Toonen, 2015. The unnatural history of Kāneʻohe Bay: coral reef resilience in the face of centuries of anthropogenic impacts. PeerJ 3 (an older case: recovery after sewage was diverted in 1979). Source

Ocean and weather data

  • NOAA Coral Reef Watch, 5 km daily heat stress products, including Degree Heating Weeks and Bleaching Alert Areas. Source
  • Copernicus Sentinel-3 OLCI ocean color products (300 m). Source
  • Copernicus Marine global ocean physics analysis and forecast. Source
  • NASA GPM IMERG precipitation. Source