Spatial and Temporal Examination of Bivalve Communities in Several Estuaries of Southern California and Northern Baja California, MX.

Anai Novoa,Nathalie B Reyns,Drew M Talley,Theresa S Talley,Jeffrey A Crooks,Erik V Thuesen

doi:10.1371/journal.pone.0148220

Abstract

A combination of historical bivalve surveys spanning 30–50 years and contemporary sampling were used to document the changes in bivalve community structure over time at four southern California and one northern Baja California estuaries. While there are limitations to the interpretation of historic data, we observed generally similar trends of reduced total bivalve species richness, losses of relatively large and/or deeper-dwelling natives, and gains of relatively small, surface dwelling introduced species across the southern California estuaries, despite fairly distinct bivalve communities. A nearly 50-year absence of bivalves from two wetlands surveyed in a Baja California estuary continued. A combination of site history and current characteristics (e.g., location, depth) likely contributes to maintenance of distinct communities, and both episodic and gradual environmental changes likely contribute to within-estuary temporal shifts (or absences). We highlight future research needed to determine mechanisms underlying patterns so that we can better predict responses of bivalve communities to future scenarios, including climate change and restoration.

Highlights

Estuarine bivalve communities have been altered through direct and indirect human effects, including overharvesting, habitat loss and alteration, pollution, the invasion of introduced species and climate change [1,2,3,4,5]
Within southern California USA and Baja California, Mexico, coastal ecosystems are impacted by heavy use, coastal development, and associated stresses, all of which have potentially influenced bivalve community structure
Intertidal salt marsh creeks were sampled within five estuaries located throughout southern California and northern Baja California, including Mugu Lagoon, Los Peñasquitos Lagoon, Mission Bay, and Tijuana River Estuary in California, USA and two distinct wetlands within Bahía de San Quintín, Baja California, Mexico (Tables 1 and 2; Fig 1)

Summary

Introduction

Estuarine bivalve communities have been altered through direct and indirect human effects, including overharvesting, habitat loss and alteration, pollution, the invasion of introduced species and climate change [1,2,3,4,5]. Within southern California USA and Baja California, Mexico, coastal ecosystems are impacted by heavy use, coastal development, and associated stresses, all of which have potentially influenced bivalve community structure. Sporadic studies over the past 50 years of bivalve communities within estuaries throughout this region indicate dramatic local shifts in intertidal bivalve communities [2,6] (and references therein). These community-level changes have likely resulted in concomitant. Examination of Bivalve Community Shifts role in study design, data collection and analysis, decision to publish, or preparation of the manuscript

Methods

Discussion

Conclusion