Persistent occurrence of floating Ulva green tide in Hiroshima Bay, Japan: seasonal succession and growth patterns of Ulva pertusa and Ulva spp. (Chlorophyta, Ulvales)

Goro Yoshida,Masayuki Uchimura,Masanori Hiraoka

doi:10.1007/s10750-015-2292-3

Goro Yoshida, Masayuki Uchimura + Show 1 more

Open Access

https://doi.org/10.1007/s10750-015-2292-3

Copy DOI

Journal: Hydrobiologia	Publication Date: Apr 29, 2015
Citations: 49	License type: CC BY 4.0

Affiliation: Fisheries Research Agency, Kōchi University

Abstract

Since the late 1980’s, a persistent green tide of floating Ulva without any clear seasonal fluctuation has occurred in Hiroshima Bay, Seto Inland Sea, Japan. We hypothesized that the persistence is due to the co-existence of Ulva species with different seasonal growth patterns, and monitored the seasonal composition and growth characteristics of the constituent Ulva within the green tide. Two morphological types of Ulva were identified, and one type, U. pertusa, was almost the sole constituent during winter and spring. The other type Ulva spp., which has marginal microscopic serrations on the thallus, was dominant during summer and autumn. Both Ulva showed the highest relative growth rate in early autumn, but growth of Ulva spp. was faster in summer than that of U. pertusa and inhibited in winter. U. pertusa had more eurythermal characteristics in which the growth rate remained relatively high in winter. Water temperature was the most correlated environmental variable for the seasonal growth of both Ulva types rather than light or nutrients, but more influential on Ulva spp. Recent increasing trend of ambient seawater temperature is considered to be favorable for the growth of both Ulva types and a causative factor of the green tide.

Highlights

Since the late 1980’s, a persistent green tide of floating Ulva without any clear seasonal fluctuation has occurred in Hiroshima Bay, Seto Inland Sea, Japan
The results enable a greater understanding of the mechanism underlying the seasonal dominance pattern of the two Ulva types and annual persistence of the green tide in Hiroshima Bay
Ulva spp. began to decrease in December and its frequency became quite low in winter and spring of 2001, when U. pertusa became dominant again and FA J AOD FA J AODF

Summary

Introduction

Since the late 1980’s, a persistent green tide of floating Ulva without any clear seasonal fluctuation has occurred in Hiroshima Bay, Seto Inland Sea, Japan. Algal taxa causing green tides, such as Ulva, Chaetomorpha, and Cladophora, can exhibit rapid vegetative growth under favorable conditions and in the floating (free-living) form. These characteristics can induce extraordinary increases in abundance and biomass accumulation of these algae along shorelines especially in enclosed sea areas, bringing serious consequences to coastal ecosystems (Den Hartog, 1994; Everett, 1994; Isaksson et al, 1994; Viaroli et al 1996a; Valiela et al, 1997; Sugimoto et al, 2007). The economic cost of the manual removal and disposal of the stranded Ulva thalli has been a concern to local governments and communities (Uchimura et al, 2004)

Methods

Results

Conclusion