Climate Change and Wastewater In Hawaii’s Coral Reefs

Coral reefs are among the most important aspects of ocean health worldwide. Considering the special connection between people of Hawaiʻi and the ocean, protecting the backbones of a healthy ecosystem is a pressing issue. Communities clustering near the shorelines of Oʻahu have a give-and-take relationship with the underwater world; whether to harvest food, connect with nature, or admire marine biodiversity. Without knowing it, humans impact coral in Hawaiʻi through wastewater pollution and lack of awareness. While no one can single-handedly reverse the effects of climate change and damage to coral, there are solutions based on known data.

Our team was formed with a common interest in the ocean and marine life, and we realized that so few people living in Hawaiʻi truly know that coral reefs are the building blocks for a healthy ecosystem. There was a lot we needed to learn to be able to display GIS data about coral in Hawaiʻi, and our group thought it was worth the time and effort because of how unique and important the reef is to the Hawaiian Islands.

These questions were our initial source of direction for where our project was headed.

1. How does coral bleaching affect the ocean? 

2. Do communities near unhealthy coral suffer from lack of food from the ocean?

3. How can mapping assist our understanding of coral decline and wastewater in coastal communities within Oʻahu from 1990-2024?”

Coral bleaching is a process in which healthy corals exert an algae known as zooxanthellae, which is responsible for many necessary processes within coral systems, such as photosynthesis. This algae typically has a symbiotic relationship with the coral they inhabit, providing the coral with food in exchange for protection. When a coral becomes stressed, usually due to environmental fluctuations, the algae leave the coral, causing it to become pale and much more susceptible to death.

The first major coral bleaching in Hawaii occurred in Kāneʻohe Bay in 1996. About 40 years earlier, raw sewage dumped into the bay had promoted green algae growth, which weakened the coral and deteriorated water quality over time. Since then, the coral reef in Kāneʻohe Bay has been victim to extreme temperature, storm flooding, and low-tide exposure. These combined factors have reduced the abundance of coral reefs and contributed to the second severe bleaching event in 2014 around Kauaʻi, Oʻahu, and Maui. In 2015, coral cover loss at surveyed sites in west Hawai‘i reached 49.7%, and the important reef-builder species --- Porites lobata, lost 55% of their population. The resilience of coral reefs in the face of today's global climate change still remains a significant concern.

Many efforts have been made to protect Hawaii's coral reefs. In 1998, the U.S. government established the Coral Reef Task Force to conduct research aimed at mitigating coral reef degradation from pollution and overfishing, and to implement conservation strategies. As part of these efforts, they expanded the Hawaii Coral Ecosystem Conservation Area. In 2018 Hawaiʻi took a significant step by officially banning the use of sunscreens containing oxybenzone and octinoxate, chemicals shown to damage coral DNA and cause infection. This act is a practical application of research findings for protecting coral. Moreover, the NOAA Office of Habitat Conservation Restoration has played a crucial role in supporting Hawaii’s marine ecosystem by investing in programs that train coral restoration professionals and contribute to the long-term restoration and resilience of coral ecosystems.

The decline in coral health is influenced by several factors, including environmental influences and human influences that put coral polyps and reef systems under stress. A decline in coral health has shown to be negative for marine ecosystems and biodiversity due to a loss of underwater structure, in addition to the communities that spend much of their time near the shoreline and use underwater resources as a way of life. With the loss of coral reefs come fewer places for biodiversity to flourish. As a result, many marine species native to the Hawaiian Islands have become endangered in the last decade alone.

The loss of reef structure points toward coastal erosion, increased atmospheric carbon dioxide, and a loss of protection for all species of reef fish. Hawaii's reefs are the first defence against natural natural disasters, reducing 97% of wave energy. The lost of one meter reef hight would double up the annual flood damages. Each of these effects will directly impact the lives of humans, especially those living in Hawai'i. Coral reefs offer over $836 million in flood protection for people, property, and jobs, while also generating more than $1.2 billion annually for the state’s economy through tourism. Communities will also suffer the loss of beloved underwater ecosystems, which impacts cultural customs and day-to-day life, such as responsible fishing and surfing.

Coral bleaching is known to be prominently influenced by fluctuations in the environment. Corals have a very particular temperature zone to thrive, typically between 73°F and 84°F. Even a few degrees over or under this distinguished range will cause polyp decay to occur, otherwise known as bleaching. This process stems from changes in SST (Sea Surface Temperature) and SFT (Sea Floor Temperature). These fluctuations come in the form of pH changes and oceanic CO ₂  levels.

Coral bleaching can also be directly influenced by man-made issues, such as Marine Debris and Wastewater Discharge. Pollution of various forms contributes to coral degradation, especially when the coral system is already in a vulnerable state. The exponential growth of Marine Debris has influenced corals by stunting growth, reducing spots for coral to take root, and chipping away at coral's appendages, which all in turn cause coral death. Wastewater influences the properties of the water it interacts with. When this wastewater reaches corals, it can be responsible for the death of large portions of the reef.

Coastal communities that are lower-income and have a disadvantage to resources are especially affected by the loss of marine diversity and fish population. The map below provides insight into the large number of communities that feel the most urgent impact.

Coral reef plays an important role in providing habitats for reef fish, and reef fish maintain the coral ecosystem by cycling nutrients, and eating algae and pests. Their interrelationship forms a healthy marine ecosystem and serves to protect the surrounding coastal communities. The coral reefs in the map are aligned with areas of higher fish catch, and dense population areas also show higher reef fish catch amounts, indicating the significant reliance on reef fish as a resource for coastal communities.

Coastal communities are particularly vulnerable to climate change and coral degradation. The decline in reef health due to wastewater can reduce fish populations, directly affecting the availability of food sources and income for these communities.

Data analysis is performed using a variety of tools and techniques. ArcGIS, an online mapping application, assists us in showcasing the problem and helps us communicate with a broad audience. The data used in our maps for sea surface water temperature is between January 2020 and February 2021. We used this data in our map to showcase the importance of using historical data.

Government

The government in Hawaiʻi can implement policy changes to ensure that geographic locations with at-risk reef sites or susceptible shorelines are limited in community development, in addition to formulating smarter zoning plans and methods of wastewater discharge.

Social

Spreading awareness in the communities is the most effective way to create personal change amongst people that impact the marine environment in Hawaiʻi. Creating opportunities for learning will turn into a positive experience for people involved in the health of coral reefs, and in some cases show a true benefit simply by making the issue noticeable.

Action

• taking the time to become educated in the issue as an individual
• notice how wastewater impacts the nearest shoreline of your community
• prevent further physical damage to coral reefs by reducing pollution or debris
• spreading helpful information to those who do not already know

In our research project, we asked marine ecosystem experts about the impact of climate change on marine biodiversity in Hawaii. Among them, Dr. Johansen, an expert in eco-physiology and behavioral ecology of coral reef fishes at the Hawaii Institute of Marine Biology (HIMB), provided valuable insights into how these species react and adapt to environmental stressors. We also received input from Jessica Glazner, a PhD student in Dr. Donahue's lab at HIMB, who offered additional perspectives on the challenges facing marine biodiversity in the region.

Dr. Johansen:

1. Corals are bleaching and dying during present day marine heatwaves, and this trend is projected in get worse as oceans warm. Simultaneously ocean acidification is slowing the growth of new coral. Combined, coral habitats are degrading, causing a loss of habitat for reef fishes and other organisms.
2. Land runoff includes sediments (which cloud the water and smother the benthos), as well as all the nutrients, pesticides and chemicals we use on land. These conditions are also life-threatening to reef organisms.

Jessica:

1. Increasing temperatures: causing mass coral bleaching, leading to significant habitat loss for coral reef inhabitants. We are losing both coral (30% over the last decade in HI) and the critters that call the reef home.
2. Storm activity: same as above, causing decline in coral cover which reduces overall biodiversity on the reef
3. Sea level rise: affects intertidal and very shallow zones the most

Dr. Johansen:

The quickest and most effective local mitigation strategy in Hawaii is likely the reduction of land-based runoff, because this is something we can fix locally. Reducing stream flow speeds and planting more trees/shrubs, particularly on steep slopes, along rivers and at the land-ocean interface will help reduce runoff by holding back erosion and keeping loose soil (and all the soil checmicals/pesticides) on the land. Mangroves are excellent at preventing and even reversing land-erosion, which is why mangroves are considered critically important almost everywhere in the world.

Jessica:

1. Legislation is in place to convert cesspools to other forms of wastewater treatment which will reduce the amount of wastewater effluent onto reefs, bolstering reef health. The goal is to convert all cesspools by 2050, so this is still in the works.
2. MPAs and fishing regulations are being implemented to protect certain areas and increase both biodiversity and biomass within the protected areas. The Kau`upulehu CBSFA is a great example of an extremely effective MPA on Hawai`i island.
3. Groups such as HIMB, TNC, DAR, Kuleana Coral, and Ako`ako`a Reef Foundation are working to increase coral cover through growing corals in nurseries and coral outplanting. Some research teams (HIMB) are working to develop corals that are more tolerant of heat stress to plant on the reef.

The End