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Human pathogens and coastal ocean processes

This project is investigating the diversity, distribution and persistence of human pathogens in the coastal marine environment of Mt. Hope Bay, Massachusetts. This estuarine environment has been heavily impacted by human activity, including significant thermal pollution, several sewage outfalls and the effects of past industrial activities. The Bay is used for recreation such as boating and fishing, but shellfishing is closed in many areas due to bacterial contamination. Although no outbreaks of human diseases, bacterial or protistan, have been reported, low levels of unreported endemic disease may persist. Monitoring for bacterial contamination occurs in the shellfish areas, but outside of these regions, very little is known about the occurrence of either bacterial pathogens or protistan parasites that are likely introduced into the Bay through sewage.

We hypothesize that both bacterial and protistan human pathogens are present in Mt. Hope Bay and nearby rivers, and that their distribution and persistence are affected by physico-chemical condition in the Bay, including the constant thermal output of the Brayton Point Power Plant.



Background

Mt. Hope Bay is located to the northeast of Narragansett Bay, with Rhode Island to the south and west and Massachusetts to the north and east. The Bay is inland and enclosed, is the sink for the second largest watershed in Massachusetts, has well defined locations of inflow and outflow and has several important sources of human impact, including sewage disposal sites and the thermal outfall of a power plant (BPPP) within a mile of each other (Figure 1). Exchange with coastal marine waters occurs only through the passages connecting the Sakonnet River and Narragansett Bay (Figure 1). Because it lies partially in two different states (Massachusetts and Rhode Island), the whole bay has not been effectively studied by either. The Mt. Hope Bay Natural Laboratory hopes to overcome this barrier in its efforts to construct new and unique approaches to addressing complex human and natural factors that influence the estuarine environment in general, and to contribute to improving public policy on estuarine management.

The Bay is currently undergoing limited monitoring for several different parameters, including fish populations, river runoff, meteorological forcing, tidal cycles and water chemistry. Descriptions of protistan diversity are generally lacking among the types of investigations that have been conducted thus far, especially in the sediments. The phytoplankton and zooplankton communities in the water column have been fairly well monitored, although not at a molecular level (see below). The MHBNL project is currently in the planning and development phase, with the identification of the most appropriate observational models being their primary goal. These models will be applied to scenario testing in the latter stages of the program, and will be used to predict the impact of annual, seasonal and episodic (natural and man-made) events on Mt. Hope Bay. In order for this to be successful, a monitoring program of the physical, biological and chemical environment over significant spatial and temporal scales is necessary.

Aims of Mt. Hope Bay Project

Aim 1: Determine the distribution & persistence of human protistan pathogens in Mt. Hope Bay.

We will conduct a molecular survey of human pathogens within the Mt. Hope Bay estuarine system, including sewage outfalls near and removed from thermal point sources, contaminated shellfish beds and shorebird nesting grounds, to better characterize the types of protistan pathogens present in this coastal environment. Our project will specifically target Giardia, Cryptosporidium, Naegleria, and Acanthamoeba, but will also perform general microbial eukaryotic and prokaryotic diversity assessments to determine whether there are novel sequence types present that are related to known pathogens (might represent unidentified human pathogens).


Aim 2: Determine whether naturally occurring marine amoebae can serve as reservoirs for pathogenic bacteria, & look for evidence of the natural occurrence of these associations in Mt. Hope Bay.

We will test whether locally collected marine amoebae are capable of harboring the pathogenic bacteria Vibrio parahaemolyticus, Vibrio vulnificus, and Legionella pneumophila. The research will test for the induced presence and replication of bacteria in actively growing and dormant phases of the amoebae, and will utilize both PCR-based and in situ hybridization based methods to detect naturally occurring associations.


Aim 3: Establish physico-chemical parameters associated with pathogen presence in Mt. Hope Bay and test predictive capability of water quality models regarding these correlations.
We will correlate measurements of water and sediment physico-chemical parameters with microbial community structure, including the presence of human pathogens. These measurements and our biological data will be used to assist in establishing and validating a water quality model for Mount Hope Bay that may also be used to understand and predict the potential presence of pathogens.


Mt. Hope Bay Natural Laboratory


Our estuaries have been impacted by human activity for several centuries, including shoreline alteration, nutrient introduction, sedimentation, toxic compound release, and thermal modification. Only in the past few decades has the public awareness of these effects resulted in regulation of these activities. Given that many aspects of human activity are very difficult to modify, it is essential to correctly understand and link observations of the results or effects with their causes. If this is not attempted, attention will likely focus on issues that are the simplest to address rather than those that are actually the most harmful.
Environmental issues are often addressed by studies that take into account one or two causal variables. Rather, a laboratory-based system would be more useful, where observations could be made, data collected and experiments formulated. This has been the driving force for the development of Mt. Hope Bay as a natural laboratory system. The program is intended to be a complete analysis of the biological and physical dynamics of the Bay, including the internal and external dynamics of the chemistry, biology and physics of the area. This will permit the ability to understand the factors that influence change in Mt. Hope Bay.

Mt. Hope Bay Natural Laboratory (MHBNL) program is a 5 year interdisciplinary project at the University of Massachusetts Dartmouth School of Marine Science and Technology (SMAST) to examine the temporal and spatial variability of the ecosystem. There is emphasis on the relative contributions of both naturally occurring and anthropogenic factors that are responsible for inducing changes to the Bay’s ecosystem. The overall goal is to determine how various processes work together to produce the ecosystem and how that ecosystem evolves. This will be a laboratory in that a variety of tools will be used for observation, experimentation and hypothesis testing. These tools include numerical modeling, incorporation of existing data and results of ongoing monitoring programs, new in situ observations, with data assimilation being the impetus that brings together all of the tools.
Mt. Hope Bay is an ideal site to base our studies of human pathogen presence and distribution. The nearby location permits effective spatial/temporal sampling and the MHBNL program provides essential infrastructure regarding estuarine dynamics and modeling.


References


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