Monitoring the Health of Commercially Important Marine Species

Specialist from Cicimar investigates how heavy metal contamination affects marine organisms through the study of the chocolata clam.

Zenaida Alzaga

Scientists from the Centro Interdisciplinario de Ciencias Marinas(Cicimar) at the Instituto Politécnico Nacional (IPN) are studying the health status of marine organisms within ecosystems that hold significant ecological and economic importance for Mexico. They aim to assess the effects of changes in environmental variables and water contamination caused by heavy metals.

Bivalve mollusks, found in soft-bottom or rocky ecosystems, play a crucial role in keeping the water column free of suspended organic matter because they are effective filter feeders. In addition to this characteristic, their status as sessile organisms (non-moving) makes them bioindicators of marine pollution.

For this reason, Dr. Jenny Carolina Rodríguez Villalobos, a researcher at Cicimar, focuses on the histopathology of marine organisms. Currently, she collaborates in the Marine Invertebrates Laboratory, where she conducts microscopic studies on the chocolata clam affected by heavy metal contamination in the Santa Rosalía area of Baja California Sur. Her findings reveal significant alterations, such as chronic inflammation and neoplasias in the tissues. Her study aims to understand the immune response of these organisms to adverse conditions through immunohistochemical characterizations in the medium term.

Dr. Rodríguez Villalobos is conducting research in the community of Santa Rosalía, located north of La Paz and designated as a Pueblo Mágico (Magical Town) in 2006. This locality depends on fishing and mining, with ongoing copper extraction from the Santa Rosalía mines.

Heavy metals naturally occur in the earth's crust, but they become concentrated in water through mining activities, where they are carried by winds and eventually end up in the sea, affecting marine life.

In Santa Rosalía, the presence of iron, copper, and tin has been detected, posing a threat to human health (depending on age and concentration) and to marine species in coastal ecosystems.

Dr. Rodríguez Villalobos explained that the chocolata clam is found at shallow depths and burrows approximately 10 centimeters into marine sediments (near the coast), from where they are extracted by divers.

The shell of this species is brown, measuring between 7 and 12 centimeters in length, with a total weight that varies depending on size and can reach up to 100 grams. However, when its coloration becomes darker, it is due to the presence of heavy metals in the water.

In parallel, the Cicimar researcher is also working on reefs and coral communities in Bahía de La Paz, particularly in the Natural Protected Areas of the Espíritu Santo Archipelago National Marine Park (PNZMAES) and the Balandra Flora and Fauna Protection Area.

In the oceans, reef-building corals represent one of the most biodiverse and productive ecosystems, such as coral reefs. In light of the El Niño event that affected the region in 2023, the scientist is monitoring the condition of corals, describing the changes in their macro and microscopic morphology.

During the El Niño 2023 event, sea temperatures were two degrees above the monthly average of previous years, turning the ocean into a warm pool associated with this phenomenon, leading to coral bleaching and even death.

Bleaching refers to the loss of coloration in corals associated with the expulsion of dinoflagellate algae, commonly known as zooxanthellae, typically when the temperature exceeds an optimal threshold for the animals. When a coral is bleached, it is not dead, but it is under extreme stress conditions that can lead to death if environmental conditions do not improve, along with its relationship with its symbiont, the zooxanthellae.

Coral reefs are found in tropical regions between 23 degrees north and 23 degrees south, representing one of the most important ecosystems within the oceans, housing a great diversity of species, including those of high commercial value for fishing. Additionally, reefs protect coastal regions as large, strong barriers that shield populations from the impacts of hurricanes and waves.

The reefs in the Pacific Ocean are experiencing higher stress levels due to suboptimal growth conditions compared to those in other parts of the world, which may make them slightly more resilient to the environmental changes caused by global warming.

The researcher noted that in recent decades, there has been a decline in live coral cover associated with bleaching events, as well as anthropogenic activities that have also contributed to the destruction of coral systems.

Therefore, the implementation of actions for the conservation of marine and coastal ecosystems is crucial today. In addition to their ecological importance, they are fundamental to the country's economy, as many sectors depend on marine resources for survival.

Selección Gaceta Politécnica #176. (July 31st, 2024). IPN Imagen Institucional: Read the full magazine in Spanish here.