Night underwater rides: the activity of a sandy beach gastropod is affected by interactive effects of light availability and water level

ABSTRACT

Olivella minuta is an abundant gastropod and important consumer on beach food webs, whose feeding activity was recently demonstrated to be reduced when submerged. Our study aimed to test the interactive effects of water level and light in the activity of O. minuta. Experiments were conducted in the laboratory simulating four conditions: (1) Light, emerged (LE); (2) Dark, emerged (DE); (3) Light, immersed (LI); and (4) Dark, immersed (DI). Our results showed a significant interaction between water level and light variation. During conditions of light availability, the results corroborated our expectations and individuals were less active when immersed. However, individuals showed the highest activity when immersed during lightless conditions. This enhanced activity on dark immersed periods can be explained by optimization of feeding strategy, to benefit from the input of food resources brought by the tide. This could also be an adaptation to avoid predation by visual predators, which needs to be further evaluated. Our results show that patterns of activity of O. minuta may be susceptible to impacts of light pollution and coastal squeezing, and that the interacting effects of light and water level need to be considered in further studies on the behaviour of beach organisms.

KEYWORDS:

• Benthic ecology
• behaviour
• subtidal
• light pollution

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPQ) via research grant (Proc. 484475/2011-8) and scholarships and research grants (Proc. 308124/2009-0; 309697/2015-8; 310553/2019-9) to AT, and the Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) via research grant to AT (Proc. 2009/17585-6) and post-doctoral scholarships to HHC (Proc. 2018/22036-0), GNC (Proc. 2017/17071-9) and LQY (Proc. 2009/15893-5). This study was also supported partially by Portuguese FCT – Foundation for Science and Technology (Project UID/Multi/04326/2019).