"But experiments indicate that human influences, such as pollution and wetland destruction, have slowly shifted the environment to encourage pfiesteria's fish-killing activity."
(experiments; indicate; that human influences, such as pollution and wetland destruction, have slowly shifted the environment to encourage pfiesteria's fish-killing activity)
experiments
indicate
that human influences, such as pollution and wetland destruction, have slowly shifted the environment to encourage pfiesteria's fish-killing activity