Seasonal and Spatial Variation of Nutrients in the Coastal Waters of the Northern Goto Islands, Japan

DOI Web Site 1 Citations

Bibliographic Information

Other Title
  • 長崎県五島列島北部沿岸海域における栄養塩の季節的・空間的変動
  • ナガサキケン ゴトウ レットウ ホクブ エンガン カイイキ ニ オケル エイヨウエン ノ キセツテキ ・ クウカンテキ ヘンドウ

Search this article

Abstract

The Goto Islands, located in the eastern-most part of the East China Sea, are one of the most famous fishing areas in Japan. In recent years, fishery yields and seaweed coverage have fallen across a wide area of the region. Moreover, coverage of seaweed beds consisting of mainly Ecklonia kurome and Sargassum macrocarpum has been markedly reduced. The present study conducted extensive spatial surveys（51 sampling stations）of inorganic macronutrients around the eastern area of the northern Goto Islands. Field surveys were conducted during four seasons : July（summer）and October（autumn）2012, and January （winter）and April（spring）2013. In summer and autumn, the PO43－ concentrations at all sampling stations were less than the detection limit（＜0．09μM）. In summer and autumn, opposite relationships between nutrients（NO3－＋NO2－ and S（i OH）4） and salinity were observed depending on the sources of the nutrients ; there were significantly negative relationships in bays that receive relatively large rivers, whereas there was a significantly positive relationship in the eastern part of the study area. These results suggest that nutrients were supplied by terrestrial runoff and regional upwelling, respectively. In winter, there was abundant NO3－＋NO2－（1．8－4．7μM）, PO43－（0．1－0．3μM）and S（i OH）4（3．9－6．7μM）, and these nutrients did not correlate with salinity. In spring, there were significantly positive relationships between salinity and nutrients（NO3－＋NO2－ and PO43－）, and a significantly negative relationship between salinity and S（i OH）4. In addition, S（i OH）4／PO43－ ratios were significantly negatively correlated with salinity, suggesting the relative importance of vertical mixing for PO43－, and terrestrial runoff for S（i OH）4. The present study suggests that although there were different nutrient supply processes depending on the season and area, continued nutrient deficiency（e.g. PO43－ throughout summer and autumn）is unfavorable for the formation of seaweed beds.

Journal

  • Bulletin on Coastal Oceanography

    Bulletin on Coastal Oceanography 55 (2), 125-138, 2018

    Coastal Oceanography Research Committee, the Oceanographic Society of Japan

Citations (1)*help

See more

Keywords

Details 詳細情報について

Report a problem

Back to top