Marine Environment and Human Health: An Overview

J. ICARUS ALLEN

ABSTRACT

The marine environment currently provides many beneficial goods and services to mankind but also poses a risk to the health of coastal populations. For example, toxic algal bloom events, microbial pathogens and pollutants all act to negatively impact human health mediated by the marine environment. At the same time, regular contact with the natural environment results in many health benefits, including increased fitness and reduced levels of stress. The marine environment is under pressure from land-derived contaminants and climate change, of which the socioeconomic consequences and the implications for human health and wellbeing are not well understood. The scientific challenge is to understand and predict the consequences of environmental changes and exploitation of natural resources upon our coastal ecosystems and upon society, including human health. Addressing this challenge requires the integration of a wide range of disciplines, from physical oceanography and marine biology, to molecular biology and epidemiology.

1 Introduction

Oceans and coastal seas form a vital part of the environment, currently providing many beneficial goods and services to mankind but also posing a risk to coastal populations. They provide a source of natural resources and are a magnet for human habitation. The marine environment's natural grandeur is a source of artistic inspiration, and yet mankind often allows it to be a sink for society's waste. Increasingly, the fragile balance of marine environments is being disrupted by the impacts of climate change and human activities. Interactions between the marine environment and humans are highly significant, diverse and complex. At the same time, the marine environment is strongly affected by the wider global environment (ocean, atmosphere and land) and is sensitive to climate change. Interactions between the atmosphere and the oceans play a significant role in the regulation of climate and weather, which in turn interact with marine environments.

Mankind benefits from the marine environment in many ways. It provides direct tangible benefits, including protein sources and economic activity associated with fisheries and aquaculture. In addition, there are the economic benefits associated with, for example, tourism, renewable energy and recreational activities. Marine ecosystems are a major source of biodiversity and a focal point for biogeochemical cycling. They play a pivotal role in the water cycle and the global biogeochemical cycling of carbon and nitrogen. Other benefits are less obvious and harder to quantify. For example, regular contact with the natural environment results in many benefits, including increased physical activity and therefore fitness, reduced levels of stress, stronger communities and an increased awareness of the value of the natural environment.

Human utilisation of the marine environment also has many negative impacts, with fisheries, industries, agriculture and aquaculture along the world's coastlines contributing to significant physical, chemical and ecological impacts on the surrounding seas. Human activity gives rise to significant inputs of pollutants and pathogens (e.g. nanoparticles, radionuclides, bacteria, viruses, nutrients and mixtures of chemical waste), in addition to natural sources (e.g. sea birds, marine mammals) to the surrounding seas. Pathogens impact directly on human health through recreational activity: for example, bathing and via shellfish into the human food chain. Both of these areas are subject to stringent regulation. Other pollutants and toxins will impact directly on marine organisms, leading to a degradation of ecosystem function and the goods and services provided in terms of carbon and macronutrient cycling, which in turn will impact on fisheries, the recreation value of the marine environment and general human wellbeing. The direct accumulation of pollutants and toxins in human food sources (e.g. shellfish) provides pathways for impact on human health. Climate change may exacerbate these effects. Seawater temperature rise may encourage the migration of Vibrio cholera and other marine bacteria, such as toxigenic Vibrios and Pseudomonads, into coastal waters. Increased run-off will also add nutrients to coastal waters, which, together with higher light intensities and temperatures, may increase the growth of toxic algal and cyanobacterial blooms. Flooding associated with sea-level rise and increased storminess may remobilise pollutants from sediments.

The impact/costs of marine environmental degradation are highly dependent on the activities and distribution of the human population and the extent/ types of waste water management and environmental regulation. It is therefore important to work towards understanding the pathways and mechanisms through which environmental hazards work and hence be able to communicate these risks to the population at large. Rapid development and unsustainable consumption of natural resources has led to an increasing complexity of environmental health hazards. For example, when an individual person living with poor sanitary conditions in an undeveloped situation consumes seafood contaminated with microbial pathogens, the effects are often apparent. The affected individual will get sick in a short time. In this case the link between cause and effect is relatively easy to measure and, crucially, to communicate. However, if the seafood is contaminated with low levels of persistent organic chemicals which may interfere with human physiology and/or reproduction, the situation is less clear cut. The links between cause and effects are much harder to demonstrate, quantify and communicate. The societal perception of risk presents another great challenge. For example, in the 1950s and 1960s there was a groundswell of public opinion that the UK's bathing waters posed a risk to human health. This was largely attributed to the discharge of untreated sewage into coastal waters. Although the supporting epidemiological evidence for a health risk was not strong, there was an overwhelming belief that swimming in dilute sewage was not healthy.

Climate change is arguably the greatest challenge facing mankind in the twenty first century. In addition to the aforementioned issues, our framework needs to take account of the potential for climate-induced changes in the marine environment.

Resulting from natural variability and anthropogenically induced changes, climate change can only be understood through improved knowledge of the coupling and feedback mechanisms between dynamic processes in the Earth system, as well as the interaction with the...