Hypernutrification in the Oligotrophic Eastern Mediterranean: A study in Haifa Bay (Israel)

N. Kress, B. Herut

Research output: Contribution to journalArticlepeer-review


This study presents the results of six cruises surveying salinity, temperature, nutrients, dissolved oxygen and chlorophyll a concentrations in Haifa Bay, Israel, covering all seasons. The outflow of the Kishon stream, in conjunction with the hydrographical conditions in the bay, are the main factors influencing water quality and the chemical characteristics in the bay. The spatial distribution of nutrients in the bay was determined by two main processes: (1) introduction of nutrient-rich waters through the Kishon estuary and their mixing with open seawater; and (2) utilization of nutrients by plankton. The immediate effect of the introduction of riverine waters into the bay was hypernutrification and the enhancement of primary productivity. Although the localized influence close to the estuary was elevated, it faded off drastically seaward to normal oligotrophic conditions. Nutrient concentrations in the bay were similar among all seasons. o-PO4 ranged between 0.02 and 29 μM, NO3+NO2 between below 0.05 and 30 μM, Si(OH)4 between 0.2 and 18 μM and NH4 between below 0.1 and 38.0 μM. Chlorophyll a concentrations, on the other hand, were seasonally dependent. Lowest chlorophyll a concentrations (between 0.2 and 3 μg-1) were found during winter, when productivity was inhibited by low temperature, while the highest concentrations (up to 48 μg l-1) were found during the spring. The productivity in the bay was found to be mostly N limited as opposed to the P limitation found in the open sea area. Median N:P ratios were similar during the whole year and ranged between 0.4 and 3.8, much lower than the Redfield's ratio and the N:P ratio of c. 26 found in the open sea area. The N limitation in Haifa Bay was probably the direct consequence of the introduction of riverine water with high o-PO4 concentrations (low N:P ratios) to the bay. During three instances, when the highest productivity was observed, probable Si limitation was also found, that was shown elsewhere to cause changes in phytoplankton population. Salinity vs o-PO4 and salinity vs N mixing lines were seasonally dependent, with no significant correlation in the winter. The mixing lines were highly significant in the summer when the outflow of the Kishon was constituted mainly of industrial and domestic effluents undiluted by fresh water. Theoretical chlorophyll a concentrations, calculated from the inorganic N vs salinity mixing diagrams, agreed with the measured values during the natural plankton bloom in the spring. A strong effort is now in progress to clean up the fiver and diminish its adverse influence on the bay.

Original languageEnglish
Pages (from-to)645-656
Number of pages12
JournalEstuarine, Coastal and Shelf Science
Issue number5
StatePublished - May 1998
Externally publishedYes

Bibliographical note

Funding Information:
The authors thank Yaron Gertner and Lora Izraelov as well as the captain and crew of the RV Shikmona, Etziona and Poseidon for their help with sampling and analysis. Chlorophyll a analysis was performed under the supervision of Dr D. Angel and Dr Y. Yacobi of IOLR. We are grateful to Hana Bernard for drawing the figures and to Keren Diskin for editing the manuscript. We appreciate the remarks of the anonymous reviewers that helped improve the manuscript. This research was funded by the Israel Ministry of National Infrastructures and by the Israel Ministry of the Environment.


  • Chlorophyll a
  • Eastern Mediterranean
  • Hypernutrification
  • N limitation
  • Nutrients
  • Seasonal variability
  • Spatial distribution

ASJC Scopus subject areas

  • Oceanography
  • Aquatic Science


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