Annual rhythms of temporal niche partitioning in the Sparidae family are correlated to different environmental variables

Valerio Sbragaglia,Jesús D Nuñez,Ernesto Azzurro,Jacopo Aguzzi,Salvatore Coco,Massimo Ponti,Davide Dominoni,Simone Marini,Joaquin Del Rio Fernandez,Emanuela Fanelli,Marc Nogueras

doi:10.1038/s41598-018-37954-0

Abstract

The seasonal timing of recurring biological processes is essential for organisms living in temperate regions. While ample knowledge of these processes exists for terrestrial environments, seasonal timing in the marine environment is relatively understudied. Here, we characterized the annual rhythm of habitat use in six fish species belonging to the Sparidae family, highlighting the main environmental variables that correlate to such rhythms. The study was conducted at a coastal artificial reef through a cabled observatory system, which allowed gathering underwater time-lapse images every 30 minutes consecutively over 3 years. Rhythms of fish counts had a significant annual periodicity in four out of the six studied species. Species-specific temporal patterns were found, demonstrating a clear annual temporal niche partitioning within the studied family. Temperature was the most important environmental variable correlated with fish counts in the proximity of the artificial reef, while daily photoperiod and salinity were not important. In a scenario of human-induced rapid environmental change, tracking phenological shifts may provide key indications about the effects of climate change at both species and ecosystem level. Our study reinforces the efficacy of underwater cabled video-observatories as a reliable tool for long-term monitoring of phenological events.

Highlights

In temperate regions, characterized by strong seasonality, the annual temporal organization of biological processes provides evident ecological advantages[1,2]
We aimed to identify how water temperature, daily photoperiod, and salinity correlate with the annual habitat use of an artificial reef by six species belonging to the Sparidae family by using 30-minute time-lapse images shot at the OBSEA cabled observatory over a three year period
D. dentex counts reached their maximum in August; D. vulgaris and D. sargus counts peaked in October and D

Summary

Introduction

In temperate regions, characterized by strong seasonality, the annual temporal organization of biological processes (i.e. phenology) provides evident ecological advantages[1,2]. Expanding the study of biological rhythms to natural contexts and to multiple species allows a comprehensive understanding of evolutionary mechanisms of phenology[13] Such an approach is complementary to more mechanistic ones in the laboratory and it may add new perspectives to track the effects of key environmental drivers such as temperature, photoperiod, and salinity on phenology of marine species. The spatial area that cabled observatories can monitor is limited, they have the advantage to enable monitoring specific habitats for very long periods of time[23,24] and in automatic way[22] In this context, the coastal Seafloor Observatory OBSEA25, has already demonstrated its value for the video-monitoring of daily activity rhythms of fishes at an artificial reef located in north western Mediterranean Sea, 4 Km off the coast and at a depth of 21 m22,26,27. The six selected species were: the common dentex, Dentex dentex (Linnaeus, 1758), the white seabream, Diplodus sargus (Linnaeus, 1758), the two-banded seabream, Diplodus vulgaris (Geoffroy Saint-Hilaire, 1817), the annular seabream, Diplodus annularis (Linnaeus, 1758), the sharpsnout seabream, Diplodus puntazzo (Walbaum, 1792), and the zebra seabream, Diplodus cervinus (Lowe, 1838)

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