Freshwater can influence marine environments in a several ways. Our goal is to understand how freshwater inputs contribute to the formation of hypoxia (very low oxygen concentrations) and dead zones in Bahia Almirante, a tropical estuary. Bocas del Toro Archipelago is a group of islands located in the northwest Caribbean coast of Panama. This group of islands create a semi-enclosed bay called Bahia Almirante with depths from 10-30 meters, which hosts coral reefs, seagrass and mangroves. Bocas del Toro is a Mission Blue Hope Spot.
HOW DOES FRESHWATER IMPACTS BAHIA ALMIRANTE?
High freshwater input into Bahía Almirante from more than 3 meters of rain per year, along with weak tidal currents results in vertical stratification during certain times of the year. Direct rainfall onto the bay as well as inputs from rivers could result in a broad freshwater ‘blanket’ which may lead to reduced vertical mixing of the water column. During stratification surface temperatures are cooler and have a lower salinity and the bottom temperatures are warmer and have a higher salinity. Low surface salinity isolates deeper water from the atmosphere, where warm temperatures and high biological oxygen demand reduce oxygen concentrations, resulting in hypoxia. In addition, nutrients, particularly from rivers laden with human-derived nutrients, can cause eutrophication, which leads to higher rates of primary production and increased oxygen consumption in the bay by microbes, further compounding the effects of stratification.
Along with stratification and eutrophication, hypoxia can form. Hypoxia is defined as dissolved oxygen (DO) concentrations less than 2mg/L. The impacts of hypoxic water on marine ecosystems are complex, but include compressing species habitat and geographical ranges, challenging the physiological capacity of intolerant species, and, in extreme cases, mass mortality or “dead zones”. In Bahía Almirante, recent low-oxygen events combined with warming have caused widespread bleaching and mortality of corals and other marine invertebrates.
As part of a larger project to understand why hypoxia develops in the bay, we are estimating the freshwater inputs into Bahia Almirante. We are measuring rainfall, to estimate how much rainfall the falls directly onto the bay. We are measuring river discharge to estimate how much river water enters the bay.
Along with stratification and eutrophication, hypoxia can form. Hypoxia is defined as dissolved oxygen (DO) concentrations less than 2mg/L. The impacts of hypoxic water on marine ecosystems are complex, but include compressing species habitat and geographical ranges, challenging the physiological capacity of intolerant species, and, in extreme cases, mass mortality or “dead zones”. In Bahía Almirante, recent low-oxygen events combined with warming have caused widespread bleaching and mortality of corals and other marine invertebrates.
As part of a larger project to understand why hypoxia develops in the bay, we are estimating the freshwater inputs into Bahia Almirante. We are measuring rainfall, to estimate how much rainfall the falls directly onto the bay. We are measuring river discharge to estimate how much river water enters the bay.