# Gametogenic Development of a Grooved Carpet Shell Clam (Ruditapes decussatus, Linnaeus, 1758) Population in the Baldaio Lagoon (N.W. Spain) Amidst Climate Change

## TL;DR

This study shows that climate change has shifted the reproductive cycle of clams in a Spanish lagoon, with warmer temperatures causing earlier spawning and altered maturation phases.

## Contribution

The study provides new insights into how long-term temperature changes affect the reproductive timing and physiology of a specific clam species.

## Key findings

- Clams started and finished their reproductive period one month earlier compared to 20 years ago.
- Warmer water temperatures correlated with changes in energy storage and reproductive maturation phases.
- Annual thermal range in the lagoon has decreased, affecting the species' reproductive patterns.

## Abstract

Climate change affects marine ecosystems, such as coastal lagoons, and therefore influences the lives of the marine invertebrates that inhabit them. In this study, we evaluated the gametogenic development of a grooved carpet shell clam population in the Baldaio lagoon (N.W. Spain). Different parameters, such as biochemical composition, condition indices, and gonadal development, were evaluated throughout the sampling period and compared with the same parameters evaluated 20 years ago. The influence of the seawater temperature of the lagoon on the results is discussed. Compared with previous data, differences in gonadal maturation were found; clams started and finished their reproductive period one month earlier and showed differences in the remaining maturation phases. Understanding these changes is an important issue to protect clam populations and a valuable aid to their management.

The impact of climate change on marine bivalves, particularly on their reproductive processes, is a current issue of concern. The aim of this study was to investigate how seawater temperatures influenced the gonadal development and overall condition of the grooved carpet shell clam (Ruditapes decussatus, Linnaeus, 1758) population in the Baldaio lagoon (N.W. Spain) over the last 20 years. Adult clams were collected, and biometric, histological, and biochemical analyses were performed. Gonadal development phases were assessed, several condition indices were calculated, water temperatures were recorded, and statistical analyses were carried out. Results indicated variations in reproductive timing, including changes in gonadal maturation, an earlier spawning period, and prolonged maturation phases, which contrasted with previous reproductive patterns described for this species. These findings coincided with thermal changes in the lagoon, where mean minimum temperatures increased and maximum temperatures decreased, and the annual thermal range was reduced in comparison with historical data (1998–1999). Biochemical composition and condition indices also reflected variations linked to temperature fluctuations, suggesting that warmer water temperatures may alter energy storage and reproduction. This highlights the importance of continuous environmental monitoring to better understand the effects of climate change on clam populations and to improve management strategies that could help to restore natural R. decussatus populations.