4
Epidemics in the Marine System
Matthias Ruth
All interest in disease and death is only another expression of interest in
life.
Thomas Mann, from The Magic Mountain
In this chapter you will learn how to:
• Disaggregate a population into individual subpopulations that interact
with each other;
• Use Conveyors to establish a specific sequencing of events for individuals in different subpopulation;
• Model the spread of a disease among members of a population;
• Conduct sensitivity analyses for your model; and
• Explore the implications of alternative model structure .
Humans influence marine ecosystems in many ways. Direct anthropogenic
impacts on marine resources include the removal of organisms such as
corals, fish, and mammals and the destruction of habitat, for example, by
off-shore drilling for oil, experimental detonation of weapons, use of poisons and explosives to stun and kill fish, incidental release of toxics, run-off
of nutrients , and impacts of fishing gear on the sea floor hab itat. Increased
anthropogenic impacts on the ecosystem may trigger indirect effects such
as elevated incidents of disease. For example, release of nutrients from
farms or sewage plants can raise nutrient concentrations in coastal areas
and tidal backwaters to an extent that fosters blooms of algae and growth
of microbes. In the presence of sufficiently high concentrations of excreta ,
some zoospores, such as Pfiesteria piscicida, are induced to become toxic.
The toxics may not only affect the behavior of fish, for example by making
them lethargic, but can directly injure their skin, inducing hemorrhaging
and bleeding, and impacting their salt balance.
Algal blooms may be toxic to fish and mammals, inducing stress to their
populations, making them more prone to diseases and/or elevating their
mortality rates. Elevated death rates of manatees CTrichechus manatus
latirostris) , for example, have been linked not only to collisions with boats,
but also to algal blooms caused by elevated nutrient levels. Stressed individuals are more susceptible of contracting disease, and are more likely to suffer
from unfavorable weather conditions, such as colder than normal winters.
54
M. Ruth et al. (Eds.), Dynamic Modeling for Marine Conservation
© Springer-Verlag New York, Inc. 2002
Epidemics in the Marine System
Matthias Ruth
All interest in disease and death is only another expression of interest in
life.
Thomas Mann, from The Magic Mountain
In this chapter you will learn how to:
• Disaggregate a population into individual subpopulations that interact
with each other;
• Use Conveyors to establish a specific sequencing of events for individuals in different subpopulation;
• Model the spread of a disease among members of a population;
• Conduct sensitivity analyses for your model; and
• Explore the implications of alternative model structure .
Humans influence marine ecosystems in many ways. Direct anthropogenic
impacts on marine resources include the removal of organisms such as
corals, fish, and mammals and the destruction of habitat, for example, by
off-shore drilling for oil, experimental detonation of weapons, use of poisons and explosives to stun and kill fish, incidental release of toxics, run-off
of nutrients , and impacts of fishing gear on the sea floor hab itat. Increased
anthropogenic impacts on the ecosystem may trigger indirect effects such
as elevated incidents of disease. For example, release of nutrients from
farms or sewage plants can raise nutrient concentrations in coastal areas
and tidal backwaters to an extent that fosters blooms of algae and growth
of microbes. In the presence of sufficiently high concentrations of excreta ,
some zoospores, such as Pfiesteria piscicida, are induced to become toxic.
The toxics may not only affect the behavior of fish, for example by making
them lethargic, but can directly injure their skin, inducing hemorrhaging
and bleeding, and impacting their salt balance.
Algal blooms may be toxic to fish and mammals, inducing stress to their
populations, making them more prone to diseases and/or elevating their
mortality rates. Elevated death rates of manatees CTrichechus manatus
latirostris) , for example, have been linked not only to collisions with boats,
but also to algal blooms caused by elevated nutrient levels. Stressed individuals are more susceptible of contracting disease, and are more likely to suffer
from unfavorable weather conditions, such as colder than normal winters.
54
M. Ruth et al. (Eds.), Dynamic Modeling for Marine Conservation
© Springer-Verlag New York, Inc. 2002