The importance of chemistry in marine ecosystem-based studies; Isabel Romero

Assessing marine ecosystems health requires multiple tools to study in an integrative way environmental pollution and impacts across different biological levels. One of the main challenges is to link physical, chemical and biological components in large-scale ecosystems when little information is available. For example, the Deepwater Horizon oil spill in 2010, contaminated the water column in the Gulf of Mexico from the epipelagic (0-200 m) to the mesopelagic (200 -1000) and bathypelagic (>1000 m) habitats; but assessment of the impact to the deep-pelagic GoM was hampered due to a lack of comprehensive data regarding diversity, abundance, distribution, and pollutants baseline-content of pelagic fauna. Several programs since the spill (e.g. DEEPEND Consortium) have improved our knowledge and understanding of the deep-pelagic ecosystem, the largest habitat in the Gulf of Mexico, and on Earth. However, information regarding the source, composition and inputs of chemical contaminants to deep pelagic fauna is still absent. Chemical contaminants can alter biological diversity and ecosystem functioning, therefore are key for linking long-term population dynamics and environmental stressors. 

As part of the DEEPEND Consortium, my role is to establish a time series of chemical composition in deep-pelagic fauna (fishes, shrimps, cephalopods) collected after the Deepwater Horizon spill. For this study, the analysis of polycyclic aromatic hydrocarbons (PAHs) was chosen because: 1) these compounds are common in crude oil; 2) are persistent in the environment; 3) their composition can be used to broadly detect the source of contamination; and 4) can be toxic to fauna. PAHs are a large group of organic compounds organized in multiple aromatic rings typically found as complex mixtures. They are present in petroleum, coal, wood, and their combustion products. When present in high amounts, for example after an oil spill in the ocean, PAHs can cause lethal and sub-lethal effects on fauna like juvenile and adult fishes, potentially increasing mortality, skeletal malformations, genetic damage, immunotoxicity, etc. 

Recently, with the collaboration of different programs, we were able to establish a decadal assessment of PAHs in mesopelagic fish tissues as indicators of environmental contamination in the deep-pelagic ecosystem. The results generated from this study indicate deep-pelagic fishes were exposed to elevated concentrations of PAHs after the Deepwater Horizon spill (2010-2011). In 2015-2016, PAH concentrations were close to the levels measured in 2007; but only for muscle tissues, because elevated concentrations were found in ovaries containing eggs. The high concentrations of PAHs found in 2010-2011 (muscle tissue), and 2015-2016 (eggs) are within the range of PAH concentrations found to cause lethal and sublethal effects on fishes. These results suggest a long-term sink for oil in deep pelagic organisms, potentially greater than shallower counterparts. Our findings demonstrate the importance of monitoring the persistence of organic contaminants in deep pelagic organisms. However, our study also indicates the need for more extensive ecosystem-based efforts of the deep-pelagic ocean (> 10 years) to better understand the long-term impacts across multiple levels of biological organization.

Here are some of the animals I am examining for PAH contamination:

     1) Cyclothone obscura; 2)  Onychoteuthis banksii,; 3) Histioteuthis corona