Biological modification of seawater chemistry by an ecosystem engineer, the California mussel,Mytilus californianus

Abstract

Marine habitat‐forming species often play critical roles on rocky shores by ameliorating stressful conditions for associated organisms. Such ecosystem engineers provide structure and shelter, for example, by creating refuges from thermal and desiccation stresses at low tide. Less explored is the potential for habitat formers to alter interstitial seawater chemistry during their submergence. Here, we quantify the capacity for dense assemblages of the California mussel, Mytilus californianus, to change seawater chemistry (dissolved O2, pH, and total alkalinity) within the interiors of mussel beds at high tide via respiration and calcification. We established a living mussel bed within a laboratory flow tank and measured vertical pH and oxygen gradients within and above the mussel bed over a range of water velocities. We documented decreases of up to 0.1 pH and 25 μmol O2 kg−1 internal to the bed, along with declines of 100 μmol kg−1 in alkalinity, when external flows were < 0.05 m s−1. Although California mussels often live in habitats subjected to much faster velocities, sizeable populations also inhabit bays and estuaries where such moderate flow speeds can occur > 95% of the time. Reductions in pH and O2 inside mussel beds may negatively impact resident organisms and exacerbate parallel human‐induced perturbations to ocean chemistry while potentially selecting for improved tolerance to altered chemistry conditions.

Role of hydrodynamics in shaping chemical habitats and modulating the responses of coastal benthic systems to ocean global change

“…For heterotrophs, respiration tends to almost exclusively lower pH in the DBL compared with the bulk seawater, regardless of day and night. Calcification and carbonate‐dissolution processes at the surface of calcareous species also change the local chemical environment of the DBL by influencing calcium content, carbonate chemistry equilibrium and total alkalinity (De Beer et al, 2000; Ninokawa et al, 2020; Roleda et al, 2012; Wolf‐Gladrow et al, 2007).…”

“…Associated species: Species belonging to the community dominated by an engineer species, living under its influence; also called "resident species" after Ninokawa et al (2020).…”

Ocean change within shoreline communities: from biomechanics to behaviour and beyond

“…At seawater velocities near zero, the respiration of mussels comprising a bed can decrease oxygen concentrations by approximately 10% (25 μmol kg −1 ) relative to control seawater (Fig. 7; Ninokawa et al., 2019). Likewise, respiration and calcification can lower seawater pH by 0.1 unit compared to surrounding waters.…”

Characterizing biogeochemical fluctuations in a world of extremes: A synthesis for temperate intertidal habitats in the face of global change

“…Diurnal cycles profoundly affect the temperature and carbonate chemistry conditions experienced by resident biota and their physiological responses (Cornwall et al, 2013; Eriander, Wrange, & Havenhand, 2015; Legrand et al, 2018; Mangan, Urbina, Findlay, Wilson, & Lewis, 2017; Moyen et al, 2019; Saavedra, Parra, San Martin, Lagos, & Vargas, 2018). This is particularly important for calcifying species as diurnal changes in habitat biogeochemistry can impact calcification–dissolution dynamics (Andersson et al, 2015; Kwiatkowski, Gaylord, et al, 2016; Leung, Connell, et al, 2017; Leung, Russell, et al, 2017; Ninokawa, Takeshita, Jellison, Jurgens, & Gaylord, 2019; Silbiger & Sorte, 2018). In shallow water marine habitats, low pH at night due to respiration can cause a decrease in carbonate mineral saturation promoting dissolution while daytime photosynthesis and associated increased pH and mineral saturation promote calcification (Kwiatkowski, Gaylord, et al, 2016; Wolfe, Vidal‐Ramirez, Dove, Deaker, & Byrne, 2018).…”