Field survey of rocky shore ecosystem in Oshika Peninsula

Fiscal Year

2014

Title

Field survey of rocky shore ecosystem in Oshika Peninsula

Project and Theme

Project 1. Study on ecological succession of fisheries ground
Representative Organization: Tohoku University
Theme2. Ecosystems and genetic researches to conserve and restore the coastal fisheries areas in Miyagi Prefecture
Representative personYukio Agatsuma
OrganizationTohoku University
DepartmentGraduate School of Agricultural Science

Research Information

Period and Interval
2014/04/01 - 2015/03/31
monthly
Research Area
Kitsunezaki beach, Oshika Peninsula
0085_R01_map00.pdf
Category
Field survey
Overview
Dynamics of population or community after the subsidence will be monitored at two areas (areaA and B) in rocky shore of Oshika Peninsula. In area A, distribution pattern of Sargassum yezoense (a species of brown algae) and two species of sea urchins: Mesocentrotus nudus and Hemicentrotus puicherrimus will ber examined, and interaction among these species will be discussed with relation to subsidence and water temperature. In area B, survival and growth of Eisenia bicyclis (brown algae) and hervivorous gastropod, Omphalius rusticus will be monitored, and their population dynamics after subsidence will be clarified in relation to various environmental factors.To clarify the effect of O. rusticus on E. bicyclis, exclosure experiment of O. rusticus will also be conducted.

Overview of the Observation

Research Point Table
Point
Namearea A_site A
Namearea A_site B
Namearea B
RemarksBase point of transect belt
Results and Future Plan
1) Eisenia bicyclis population dynamics: Survival rate of adult Eisenia didn't differ between shallower site and deeper site in the study area. However, growth of Eisenia at deeper site stagnated while Eisenia at shallower site grew. Juvenile Eisenia recruitments were observed after increase of nutrient concentration, suggesting that nutrients might promote sporophyte emergence. On the other hand, light intensity and sea water temperature variations didn't show clear relation to the juvenile recruitment. 2) Genetic structure of Eisenia population: Sampling of specimens from every individuals in the study area for genetic analysis have been done. We will began genetic analysis soon after the primer sets will be prepared. 3) Omphalius rustics: Shell diameter histograms of O. rusticus had three modes and showed juvenile recruitment in September. Annual survey on gonad maturation index indicates its reproductive season in July to September. Our data also suggest that this snail becomes visible size in their first year after birth, and rapidly grow to maturation size in their second year, then reduce their growth rate. Based on this growth rate decrease, the largest size mode in the size histogram might consist of several cohorts, and the life span might be more than 3 years. A field exclusion experiment of O. rusticus are being conducted now, and we will get some knowledge about this snail's feeding pressure to sea weed.

Investigation Item and Data Acquisition

Investigation ItemData Acquisition
Sargassum yezoenseabundance and annual life cycle of Sargassum yezoense in area A.
sea urchinmonthly data of density, size destribution, age, growth, gonadal development, and gonad color of Stronglycentrotus nudus and Hemicentrotus puicherrimus in area A
Eisenia bicyclissurvival and growth data of Eisenia bicyclis in area B
Omphalius rustcusmigration, survival and growth data and results of exclusion experiment of Omphalius rustcus in area B
environmentilluminance, water temperature, salinity, current direction and speed, and turvidity in area B

Reference

Related Observation Plan
FY2014 Field survey of rocky shore ecosystem in Oshika Peninshura

Person in charge of Investigation

Representative personMasakazu N. Aoki
OrganizationTohoku University
DepartmentGraduate School of Agricultural Science

Keywords

Fiscal Year2014
OrganizationTohoku University
CategoryField survey
Research AreaIshinomaki Bay
DisciplineOcean physics -> Water temperature
Ocean physics -> Salinity
Ocean physics -> Ocean current / Tidal current (Current direction/Current speed)
Ocean physics -> Others
Ocean chemistry -> Salinity
Ocean chemistry -> Dissolved oxygen
Ocean chemistry -> Nutrients
Ocean environment -> Nutrients
Ocean environment -> Plant pigments
Ocean biology / Ocean ecology -> Biomass
Ocean biology / Ocean ecology -> Ecology
Ocean biology / Ocean ecology -> Sea algae
Ocean biology / Ocean ecology -> Mollusks
Ocean biology / Ocean ecology -> Others
Topography / Geology / Geophysics -> Bottom sediment