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Causes of Outbreak Pelagia noctiluca in M'Diq Beach, Northwest Moroccan Mediterranean Coastline


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The M'Diq beach has seen a successive outbreak's of starting in 2011. During the summer season, which is also Pelagia noctiluca known as the blooming and stranding's jellyfish season has severe impacts on regional activities. For this reason, this research aimed at documenting the mean causes of outbreaks on our coastline. As a result, the simple linear tests shows that outbreaks P. noctiluca P. noctiluca have a very significant linear relationship and are positively correlated to sea surface temperature with P= 0.0079 with y = 3.5254x-59.616, R² = 0.2062, sea salinity P= 0.0029 with y =14.741x-507.54, R² = 0.2517 and waves high P= 0.000000002 with y = 20.473x-4.4583, R² = 0.6893. Moreover, the blooms of jellyfish along with the production of Pelagic fish and whitefish were respectively and share a strong correlation with P= 0.000001936, with y =-0.0079x + 40.881, R² = 0.5063 for Pelagic fish and y =-0.0323x + 55.431, R² = 0.3008 for whitefish production.
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Causes of Outbreak in M'Diq Beach, Pelagia noctiluca
Northwest Moroccan Mediterranean Coastline
Indian Journal of Ecology (2021) 48(2): 519-523
Manuscript Number: 3245
NAAS Rating: 5.79
Abstract: The M'Diq beach has seen a successive outbreak's of starting in 2011. During the summer season, which is also Pelagia noctiluca
known as the blooming and stranding's jellyfish season has severe impacts on regional activities. For this reason, this research aimed at
documenting the mean causes of outbreaks on our coastline. As a result, the simple linear tests shows that outbreaks P. noctiluca P. noctiluca
have a very significant linear relationship and are positively correlatedto sea surface temperature with P= 0.0079 with y = 3.5254x - 59.616, R²
= 0.2062, sea salinity P= 0.0029 with y =14.741x - 507.54, R² = 0.2517 and waves high P= 0.000000002 with y = 20.473x - 4.4583, R² = 0.6893.
Moreover, the blooms of jellyfish along with the production of Pelagic fish and whitefish were respectively and share a strong correlation with
P= 0.000001936, with y = -0.0079x + 40.881, R² = 0.5063 for Pelagic fish and y = -0.0323x + 55.431, R² = 0.3008 for whitefish production.
Keywords: Jelly fish, Blooms, Fisheries productions, Moroccan Mediterranean northwest coastlinePelagia noctiluca,
Majda Aouititen, Aravinda Ravibhanu Mohammed Mrhraoui and Xiaofeng Luan
1, 2
School of Ecology and Nature Conservation, Beijing Forestry University, Beijing 100083, China
1Department of Research & Innovation-Eco Astronomy Inc, Colombo, Sri Lanka
2National Institute of Fisheries Research Tangier-M'Diq-Morocco
It is undeniable that long-term climatic change will
influence the increase of jellyfish outbreaks, as weather
factors such as temperature and precipitation change (Hecq
et al 2009, Aouititen et al 2019). Some theories mentioned
the impact of some hormone pollutants discharged into the
ocean; notably, estradiol contained in drugs for the treatment
of menopause and contraceptives, themselves included in
human urine as well as the insecticide impacts (Dhawan et al
2012), case study observed of the insecticides toxicity on the
marine crustacean the brine shrimp (Nwokwu Gilbert
Nwogboduhu 2017); that would result in mutations in fish.
Although in tiny quantities, these potent hormones can
influence the sexual development of fish, the loss of male fish
reduces breeding opportunities and can exacerbate
declining fish populations leading to a proliferation of jellyfish.
Pelagia noctiluca, because of their capacity for budding and
asexuality, do not fear these hormones. If global warming
persists in the years to come, jellyfish populations will likely
increase dramatically in all the world's seas and oceans.
Increasing jellyfish populations will directly damage fish
populations through predation and competition. The decline
of fish numbers risks becoming a vicious circle, although the
port of M'Diq is an excellent sardine port, in 2011 there was an
alarming indication of a real depletion of the stock. The
economic contribution of this type of fishing is becoming
increasingly small.
Moreover, the massive appearances of the scyphozoan
jellyfish are becoming more frequent in the P. noctiluca
western Mediterranean. The jellyfish stranding is interfering
with fishing by plugging fishnets and competing with fish for
food (Kogovšek et al 2010, Daly et al 2010). According to
some observations, "jellyfish can also kill fish and their larvae
in aquaculture pens, or clog the pipelines of desalting and
power plants" ( ). Another problem Malačič et al 2007
observed during surveys where fishers would cast their
fishing nets, a large number of jellyfish can become ensnared
with the fish become pulverized and contaminated the edible
fish, reducing the market value of the catch. is a P. noctiluca
crucial "non-selective planktonic predator feeding on almost
all types of zooplankton and ichthyoplankton" (Daly et al
2010, Rosa et al 2013). Many types of fish, such as reef fish
species, as well as pelagic fish species eating ephyrae and
small individuals, compete for the same zooplankton prey as
jellyfish (Graham 2001, ). As argued Purcell et al 2001 2007
here, the declination of those fishes will open up ecological
niches for jellyfish proliferation ( 2004,Lynam Purcell et al
2007). The objective of this research is to understand the
causes of outbreaks observed since 2011 Pelagia noctiluca
in the Moroccan Mediterranean coastal. Besides, the
importance of this research is to document and to highlight as
well the severe impact that jellyfish outbreaks have on
fisheries production.
Study area: M'Diq is known as a seaside city, located at the
geographical coordinates 35° 41'N, and 5° 19 '31 W. Fishing
and summer tourism are the mean economic resources for
the local population. M'Diq covers an area of 480 hectares, of
which 153 hectares are urbanized. The city is located 7 km
from Tetouan city, and it is bounded on the east by the
Mediterranean Sea (Aouititen et al 2019). The selection of
this area to conduct the research is due to the critical
numbers of outbreaks recorded. The existence of P. noctiluca
permanent surface currents characterizes the marine
hydrology in this area, and continuous flow from west to the
east brings Atlantic waters into the Mediterranean,
compensating for losses by evaporation and which result in
heavy salinization. The winds are sometimes violent and play
a role in the disturbance of these surface currents, creating
currents opposite to those described above. The tides are of
low amplitude, with the highest reaching barely two meters,
and they generally remain poorly perceived because of the
steep slope of the shoreline . (Dakki 2004)
Sampling strategy: P. noctilucaFrom 2011 to 2017, was
collected daily during each blooming season to conduct
biometric measurements (Fig. 1). The selected transect in
M'Diq was between the low tide and high tide limit. The
transect start and endpoints were recorded and described as
follows: "start: 35.683160 N, -5.319175 W; 35.698070 N, -
5.328777 W; length: 963m". The variation in the production of
pelagic and whitefish data in the M'Diq port was collected
from the Moroccan national office of fisheries. The waves
high were recorded from Copernicus online database. Sea
surface temperature, as well as sea surface salinity, was
recorded in situ (independent points) for each survey
(Aouititen et al 2019). Both of these parameters have been
recorded from June 2011 until December 2017 during each
jellyfish stranding day, and a monthly average used for
correlation analyses with jellyfish abundance. The
calculation of jellyfish stranded density per square meter was
performed by using a quadrate method (Aouititen et al 2019).
Fig. 1. The geographical location of our study area
Source: Google Map
Cluster analysis: The data obtained from the samples were
statistically analyzed using SPSS 25 and Microsoft Office
Excel 2010. Simple linear regression and ANOVA analysis
was used to investigate whether there is a relationship
between the quantitative variable, which is sea surface
salinity, temperature, waves high and for both Pelagic fish
and Whitefish production in the M'Diq port and the changes of
P. noctiluca density during the blooming seasons to
understand which type of correlation they share.
The simple linear regression analysis proved that there
is a strong significant relationship between the blooms of P.
noctiluca collected and the high sea surface temperature
recorded since 2011 till 2017 (Table 1). The P-value were P <
0.05, P= 0.007937422. Moreover, that these two parameters
are correlated positively, which means when the sea surface
temperature rises, then the outbreaks of our jellyfish will
increase as well, with y = 3.5254x - 59.616, R² = 0.2062 (Fig.
Scientists proved that sea temperature could influence
jellyfish life cycles and its reproductive process (Purcell et al
2007, Boero et al 2008 Seawater temperature, together ).
with available resources of nutrients, were essential drivers
of gonads development (Ben-David-Zaslow and Benayahu
1999). The increase in temperature is considered to be a key
factor for the successful reproductive processes of P.
Sea Surface Salinity (SSS) and jellyfish blooms: In Table
1, the simple linear regression analysis along with ANOVA
test has proved as well that there is a very significant
relationship between the blooms of Pelagia noctiluca
collected and the sea surface salinity recorded from 2011 till
2017 as it showed the P-value found to be P < 0.05, P=
0.002931034. Besides, we have found that these parameters
correlated positively, which mean when the sea surface
salinity increase then the blooms of our jellyfish will increase
as well; with y =14.741x - 507.54, R² = 0.2517 (Fig. 3).
Between 1976 until 1983, a research conducted by Tegaccia
(1983) mentioned as well that the highest densities of P.
noctiluca in the Adriatic Sea were recorded with high salinity
and low nutrients.
Sea waves high and jellyfish blooms: After testing the
relationship between Sea waves high and jellyfish blooms
density using a simple linear regression analysis along with
ANOVA test (Table 1) we have found that there is a significant
strong relationship; as it showed the P-value was found to be
P < 0.05, P= 0.0000000023. In fact, these parameters are
found to share a positive correlation, which means when the
waves start to be higher as results, the blooms of Pelagia
520 Majda Aouititen, Aravinda Ravibhanu, Mohammed Mrhraoui and Xiaofeng Luan
15 17 19 21 23 25 27
Sst (°C)
Fig. 2. Simple linear regression analysis of sea surface
temperature (SST) and jellyfish blooms density
34.5 35 35.5 36 36.5 37 37.5
SSS (Psu)
Fig. 3. Simple linear regression analysis of Sea Surface
Salinity (SSS) and jellyfish blooms density
0 1 2 3
Wave height (m)
Fig. 4. Simple linear regression analysis of Sea waves high
and jellyfish blooms density
Regression statistics Correlation between SST &
jellyfish blooms density
correlation between SSS &
jellyfish blooms density
Correlation between Sea waves high &
jellyfish blooms density
Multiple R 0.45412688 0.50173889 0.830223056
R Square 0.20623122 0.25174192 0.689270323
Adjusted R Square 0.18062578 0.22760456 0.679246785
Standard error 14.6319741 14.2063211 9.154766775
Observations 33 33 33
SS 1724.360006 2104.888361 5763.192295
MS 1724.36 2104.888 5763.1923
F 8.054194 10.42956 68.76517
Significance F 0.007937422 0.002931034 2.2895E-09
Table 1. Simple linear regression and ANOVA analysis of the correlation between Sea waves high and jellyfish blooms density
noctiluca will increase in our shoreline; with y = 20.473x -
4.4583, R² = 0.6893 (Fig. 4).
Aouititen et al (2019) concluded that waves high as well
as Est wind could lead to the prediction of jellyfish stranding in
the Moroccan Northwest Mediterranean coastline.
Pelagic fish and Whitefish production and jellyfish
blooms: There is a significant relationship, as it showed the
P-value found to be P < 0.05, P= 0.000001936 (Table 2).
However, these parameters were found to be negatively
correlated, which mean when the Pelagic fish and whitefish
production start to decrease then the blooms of P. noctiluca
will increase in our area of study; with y = -0.0079x + 40.881,
R² = 0.5063 for Pelagic fish production and y = -0.0323x +
55.431, R² = 0.3008 for whitefish production and blooms of
our jellyfish (Fig. 5).
Outbreaks of were reported in 2007 to cause P. noctiluca
mortalities of farmed fish in northeast Ireland and on the
Scottish west coast (Doyle et al 2008). The outbreaks of P.
noctiluca appear to be associated with affecting fish and
521Causes of Pelagia noctiluca Outbreak
1500 2500 3500 4500 5500
Weight per ton of Pelagic
fish in M'diq port
650 850 1050 1250 1450
Weight per ton of White
fish in M'diq port
Fig. 5. Simple linear regression correlation between weight
per ton of Pelagic and Whitefish with Pelagia
noctiluca blooms density
Groups Count Sum Average Variance
Pelagia noctiluca emalesf 7 127.339 18.19129 173.119256
Pelagia noctiluca alesm 7 20114 2873.429 1405746.29
Pelagia noctiluca uvenilej 7 8061 1151.571 49790.619
Source of ariationv SS df MS F P-value F crit
Between roupsg 28937353 2 14468676 29.8177715 1.93601E-06 3.554557146
Table 2 . ANOVA analysis between Pelagic fish and Whitefish production with jellyfish blooms density
Fig. 6. Pelagia noctiluca trapping and in the process of
swallowing a small fish
zooplankton abundance by preying on fish larvae and
competing for nutrients (Purcell 2001, Lynam et al 2005). P.
noctiluca is an important planktonic predator of fish larvae so
they can affect fish larval abundance (Fig. 6) (Daskalov et al
2007, Purcell et al 2007).
In this research study, we found that sea surface
temperature with P= 0.007937422, sea salinity P=
0.002931034 as well as waves high P= 0.0000000023
positively correlated to outbreaks on our Pelagia noctiluca
area of study; those parameters are the principal causes which
lead to the blooms of jellyfish along our Moroccan
Mediterranean northwest coastal. Apart from this, the
production of Pelagic fish and whitefish was recorded to have
a negative correlation with jellyfish stranding, and it was found
to be very significant P= 0.000001936, which means when the
production of Pelagic fish and whitefish decrease, we are
going to observer significant outbreaks of . As Pelagia noctiluca
a consequence, we predicate not only to observe consecutive
long blooming seasons but as well we may document a long-
term decrease in marine stocks of fish in our area.
We declare that Ms. Majda AOUITITEN has collected,
analyzed the data, and wrote the paper. Dr. Mohammed
MRHRAOUI provides us with a laboratory where we
conducted some of our analysis and Dr. Aravinda
RAVIBHANU as well as Pr. Dr. Xiaofeng LUAN reviewed the
manuscript. We would like to address our sincere appreciation
for all the motivation and support we've received from Mrs.
Jamila Semlal.
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Received 26 October, 2020; Accepted 25 December, 2020
523Causes of Pelagia noctiluca Outbreak
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Full-text available
Although recent articles state that jellyfish populations are increasing, most available evidence shows that jellyfish abundances fluctuate with climatic cycles. Reports of increasing prob- lems with jellyfish, especially in East Asia, are too recent to exclude decadal climate cycles. Jellyfish are infamous for their direct negative effects on human enterprise; specifically, they interfere with tourism by stinging swimmers, fishing by clogging nets, aquaculture by killing fish in net-pens and power plants by clogging cooling-water intake screens. They also have indirect effects on fisheries by feeding on zooplankton and ichthyoplankton, and, therefore, are predators and potential competitors of fish. Ironically, many human activities may contribute to increases in jellyfish populations in coastal waters. Increased jellyfish and ctenophore populations often are associated with warming caused by climate changes and possibly power plant thermal effluents. Jellyfish may benefit from eutrophication, which can increase small-zooplankton abundance, turbidity and hypoxia, all conditions that may favor jellyfish over fish. Fishing activities can remove predators of jellyfish and zooplanktivorous fish com- petitors as well as cause large-scale ecosystem changes that improve conditions for jellyfish. Aquacul- ture releases millions of jellyfish into Asian coastal waters yearly to enhance the jellyfish fishery. Aquaculture and other marine structures provide favorable habitat for the benthic stages of jellyfish. Changes in the hydrological regime due to dams and other construction can change the salinity to favor jellyfish. Accidental introductions of non-native gelatinous species into disturbed ecosystems have led to blooms with serious consequences. In many coastal areas, most of these environmental changes occur simultaneously. We summarize cases of problem jellyfish blooms and the evidence for anthropogenic habitat disruptions that may have caused them. Rapid development in East Asia makes that region especially vulnerable to escalating problems. We conclude that human effects on coastal environments are certain to increase, and jellyfish blooms may increase as a consequence.
Full-text available
An oceanic cruise (October 2007) revealed the widespread occurrence of Pelagia noctiluca in the NE Atlantic just prior to a major fish kill induced by P. noctiluca in Irish coastal waters. Constrained by a benthic polyp stage, most scyphozoan jellyfish have a predominantly coastal distribution. However, the scyphozoan Pelagia noctiluca lacks a benthic polyp stage and this species consequently has a very broad distribution across ocean basins (Arai, 1997; Purcell, 2005). Pelagia noctiluca is well known for its major outbreaks in the Mediterranean where it impacts negatively on both fisheries and tourism (CIESM, 2001). The impact of these blooms on fish populations may be considerable as P. noctiluca is a top planktonic predator (Larson, 1987), feeding on almost all zooplank-ton (Giorgi et al., 1991; Zavodnik, 1991; Malej et al., 1993), including eggs and larvae of nekton. Pelagia noctiluca may also cause fish mortalities in aquaculture cages possibly by irritating the fish gills (Merceron et al., 1995). Considering this notoriety, there are compara-tively few published records of P. noctiluca blooms outside the Mediterranean. Here we document the widespread occurrence of P. noctiluca in the NE Atlantic, just prior to a major fish kill induced by P. noctiluca, and discuss the historical occurrence and likely impacts of climate change for this species. Net tows and visual observations for P. noctiluca were carried out during a cruise from 30 September to 22 October 2007 on board the RV Pelagia (Royal Netherlands Institute for Sea Research; NIOZ). Net tows, visual observations and dip netting were con-ducted in seven main areas of the slope and shelf waters west of Ireland (Fig. 1). Visual observations for P. noctiluca were also conducted when in transit between these areas when weather permitted. Vertical net tows were carried out from 200 m to the surface, using a 1 m diameter ring net with a 700 mm mesh towed at 0.5– 1 m s 21 . Given the large mesh size and the fact that no large catches were made that could possibly clog the net, we assumed 100% filtration efficiency. All P. noctiluca were counted and bell diameter measured to the nearest mm immediately after collection. All net tows were deployed independent of surface observations, and all locations were randomly selected depending on doi:10.1093/plankt/fbn052, available online at
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Jellyfish medusae prey on zooplankton and may impact fish recruitment both directly (top-down control) and indirectly (through competition). Abundances of Aurelia aurita, Cyanea lamarckii and Cyanea capillata medusae (Scyphozoa) in the North Sea appear to be linked to large-scale inter-annual climatic change, as quantified by the North Atlantic Oscillation Index (NAOI), the Barents Sea-Ice Index (BSII) and changes in the latitude of the Gulf Stream North Wall (GSNW). Hydroclimatic forcing may thus be an important factor influencing the abundance of gelatinous zooplankton and may modulate the scale of any ecosystem impact of jellyfish. The population responses are probably also affected by local variability in the environment manifested in intra-annual changes in temperature, salinity, current strength/direction and prey abundance. Aurelia aurita and C. lamarckii in the north-west and south-east North Sea exhibited contrasting relationships to change in the NAOI and BSII: north of Scotland, where the North Sea borders the Atlantic, positive relationships were evident between the abundance of scyphomedusae (data from 1974 to 1986, except 1975) and the indices; whereas west of northern Denmark, a region much less affected by Atlantic inflow, negative relationships were found (data from 1973 to 1983, except 1974). Weaker negative relationships with the NAOI were also found in an intermediate region, east of Scotland, for the abundance of A. aurita and C. capillata medusae (1971 to 1982). East of Shetland, the abundance of jellyfish was not correlated directly with the NAOI but, in contrast to all other regions, the abundances of A. aurita and C. lamarckii (1971 to 1986, not 1984) were found to correlate negatively with changes in the GSNW, which itself was significantly positively correlated to the NAOI with a two year lag. On this evidence, we suggest that, for jellyfish, there exist three regions of the North Sea with distinct environmental processes governing species abundance: one north of Scotland, another east of Shetland, and a more southerly group (i.e. east of Scotland and west of northern Denmark). Impacts by jellyfish are likely to vary regionally, and ecosystem management may benefit from considering this spatial variability.
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: Pronounced interannual variability in the abundance of medusae of the jellyfish species Aurelia aurita, Cyanea lamarckii, and Cyanea capillata (Phylum Cnidaria, Class Scyphozoa) in the North Sea was evident in data arising from the International Council for the Exploration of the Seas International O-group Gadoid Surveys between 1971 and 1986. Possible climatic forcing of jellyfish abundance, via the North Atlantic Oscillation (NAO), was investigated with data on medusae from four areas of the North Sea (east of Scotland, north of Scotland, east of Shetland, and west of northern Denmark). There were significant inverse relationships between medusa abundance and the NAO Index (December-March) in two regions: west of northern Denmark (A. aurita r(2) = 0.70, P = 0.003, n = 10; C lamarckii r(2) = 0.74, P = 0.002, n = 10) and east of Scotland (A. aurita r(2) = 0.53, P = 0.008, n = 12). Fluctuations in the abundance of A. aurita and C. lamarckii medusae might be linked to hydroclimatic changes induced through atmospheric effects (as encapsulated in the NAO Index) on wind stress, temperature, and currents. These fundamental hydroclimatic changes alter the timing of spring phytoplankton blooms and zooplankton community composition. Predation by an abundance of medusae on zooplankton and ichthyoplankton could affect the North Sea ecosystem through top-down and bottom-up mechanisms. Because the NAO is presently in a high phase, climatic conditions could be serving to depress the abundance of medusae: a future reversal of the NAO might favor jellyfish and weaken the persistence or recovery of fisheries.
Full-text available
In spite of being one of the most relevant components of the biosphere, the plankton-benthos network is still poorly studied as such. This is partly due to the irregular occurrence of driving phenomena such as gelatinous plankton pulses in this realm. Gelatinous plankters rely on their life cycles and histories to exploit temporarily abundant resources with an undeniable, but often overlooked, impact on marine food webs. Dramatic increases of gelatinous filter-feeders and/or carnivores (both native and nonindigenous species) are frequently observed, and explanations of these blooms alternatively invoke ecosystem variability, climate change, unspecified anthropogenic perturbation or removal of top predators from trophic networks. Gelatinous plankters, however, are not anomalies in plankton dynamics: the recognition of the ecological importance of their pulses, based on their life cycle patterns (often involving benthic stages), is a critical breakthrough to understand the cycling diversity of plankton in space and time. The current study focuses on the many neglected aspects of the ecology and biology of gelatinous zooplankton, describes how life cycle patterns are central in marine ecology, as are the pulses of gelatinous organisms, and highlights how such a dramatic lack of knowledge can affect our understanding of the marine ecosystem as a whole.
Toxicity of one herbicide and two insecticides were determined using the marine crustacean Artemia salina called the brine shrimp. The brine shrimp larva were hatched in the laboratory and were exposed to five concentrations of the atrazine, nicotine and imidacloprid at 6 and 24 hours..The dose-response of the brine shrimp larva to the toxicants increased with the Increasing time of the exposure and also the mortality increased. The LD50 decreases untill it levelled off and the acute toxicity of the insecticides were similar. The LD50, of the Imidacloprid for 6 and 24 hours were 3.58 and 1.77 ppm, LD50 of nicotine for the same 6 and 24 hours were 3.73 and 2.49 ppm while the least toxic was atrazine and the LD50, were 17.12 and 3.14 ppm. The result of this study revealed that the pesticides were toxic to the brine shrimp larvae except the control.
To identify some of the possible environmental factors stimulating the increasingly frequent outbreaks of the scyphomedusa Pelagia noctiluca in the Straits of Messina, we investigated its abundance, growth, reproduction and feeding over a 4-year period, from 2007 to 2011, at two coastal sites. Using either field investigations and manipulative experiments we show that, among the various factors considered, shifts in water temperature (influencing medusae metabolism, growth and reproduction rates) and the size structure of the zooplankton community (their natural preys) can promote the proliferation of P. noctiluca. In particular, we show that increased temperature let jellyfishes to grow more rapidly and reach exceptional sizes. We also report a peculiar opportunistic behavior of P. noctiluca, which makes this species a potentially strong competitor in the pelagic trophic web of the Straits ecosystem. We therefore propose that more frequent P. noctiluca outbreaks stimulated by increasing sea surface temperature and shifts in their prey availability and composition would become, in the near future, a major cause of ecosystem shift.
Heteroxenia fuscescens is a common zooxanthellate soft coral on the shallow reefs of the Gulf of Eilat, northern Red Sea. Its main nutritional sources are the uptake of dissolved organic material (DOM) and carbon fixation by its symbiotic algae (zooxanthellae). Recent studies have indicated that although colonies of H. fuscescens release planulae all year round, their fecundity was subject to seasonal changes. In this study the monthly per cent of ash, lipid, protein and carbohydrate in the coral tissue over a three year period was determined. It was found that the tissues of colonies of H. fuscescens contained a monthly per cent mean of 8.8±4 ash (without sclerites), 11±3.5 lipid, 19.2±6.4 protein, and 0.6±0.01 carbohydrate (N=36). This study is the first to present such values based on long term investigation of the biochemical profile of a coral, thus enabling an examination of temporal variability in biochemical composition among seasons and successive years. The results indicated seasonal fluctuations in lipid and protein content, while variation in the biochemical composition among years was expressed only in the protein content. The mean energetic content of H. fuscescens was relatively high at 23.3±1.2 kJ g−1 dry weight (DW). A significant difference in the energetic content of H. fuscescens was found among seasons. It is suggested that the increase in nutrient levels following the annual mixing event at the Gulf of Eilat and the raised light levels led to high energetic content during summer, which may reflect the increase in the number of embryos and developing planulae in H. fuscescens colonies. Furthermore, it is suggested that in the Gulf of Eilat seasonal fluctuations in the abiotic features of the water may have an impact on the biochemical composition and energetic content of the studied species.