Abstract: The present study is a first attempt to examine sponge distribution in the Persian Gulf (Iranian costs) and suggests that physical and biological factors influence the sponge distribution patterns in Hengam Island. The purpose of this study is to provide patterns of sponges distribution and depth influence on sponge abundance and biomass on the Hengam Island. Surveys of sponge distribution were conducted June 2006 and February 2007 at 5, 10, 15 and 20 m depths sites in two locations: East and West of the Hengam island. Abundance and biomass of sponges species were surveyed at different depths on the Hengam Island in the Persian Gulf. All data on sponges species number and abundance and biomass in each region of Island were taken by SCUBA diving. Transect sampling in this area revealed distribution of sponges species. The sponges species in this area consist of Callyspongia clavata, Callyspongia vasselli, Hyrtios erectus, Haliclona sp., Leucetta sp., Ircinia echinata and Dysidea cinerea. Abundance and biomass of sponges in Hengam Island increased at 15-20 m depths.
INTRODUCTION
Sponges are an important component in many benthic communities and can dominate the benthos in some regions in terms of biomass and diversity (Schmahl, 1990a; Wilkinson and Cheshire, 1990; Duckworth and Wolff, 2007). Sponges are found from deepest oceans to the edge of the sea (Hooper, 2000). Distribution patterns of sessile organisms such as sponges may vary (Duckworth and Wolff, 2007). Environmental parameters are well known to influence sponges distribution (Diaz et al., 1990; Schmahl, 1990b; Alcolado, 1990; Bell and Smith, 2004). Environmental and biological factors can also generate randomness in sponge distribution (Zea, 2001). However, within most habitats a suite of biological and physical factors are likely to be responsible for any individual species abundance and distribution pattern, rather than any particular variable (Bell and Smith, 2004). Wilkinson and Cheshire (1989) and Zea (2001) believed interaction of physical, biological and stochastic factors influencing the distribution and abundance of individual species. The abundance and distribution patterns of sponges can be influenced by water flow and depth (Wilkinson and Evans, 1989; Roberts and Davis, 1996; Duckworth and Wolff, 2007), tidal height (Barnes, 1999), predation (Dunlap and Pawlik, 1996), light (Cheshire and Wilkinson, 1991) and substrate and habitat type (Adjeroud, 1997; Duckworth and Wolff, 2007). The influence or impact of each factor varies among sponge species, often restricting species to specific area or depth (Wilkinson and Evans, 1989; Duckworth and Wolff, 2007). To date, no published reports are available on sponges distribution patterns from Iranian coasts of Persian Gulf. This study is the first report of sponge distribution in this area. Based on the above-mentioned information, purpose of the present study is to examine distribution of sponges and study of depth parameter influence on sponges abundance and biomass in Hengam Island.
MATERIALS AND METHODS
Hengam Island (Fig. 1) is located in the Hormoz strait
mouth on the Persian Gulf waters (at 55°54´40"-55°54´55" E and
26°36´43"-26°41´15" N). Qeshm and Larak Islands are located of
the north and northeast of the Hengam Island. Length, width and area of
this Island is about 9.8, 3-6 km and 50 km2, respectively.
In Hengam Island, major substrates to sponges are sand, respectively rock,
sandstone, mud and coral reef (Hafezniya, 2003). Surveys of sponge distributions
were conducted in June 2006 and February 2007 at 5, 10, 15 and 20 m depths
sites in two locations of Hengam Island (East (55°54´33" E, 26°38´56"
N) and West (55°51´37" E, 26°39´29" N)). Three 20x1 m transects
were examined at each depth, with each transect separated by at least
20 m. By SCUBA diving all obvious sponges within each transect were collected
and weighed (wet). Number of sponges specimens of each species were recorded
in each depth on the East and West of the Hengam Island. Single ANOVA
were used to examine different in sponge abundance and biomass data among
depths.
| Fig. 1: | Map of Hengam island |
RESULTS AND DISCUSSION
Analysis variance on individual abundance and sponge biomass on two region of Hengam Island shows significant relation to depth. Sponge individual abundance and biomass increase with depth on Hengam Island (Table 1). Abundance of sponge species varied significantly between depths on two regions of Island (Table 1), with more individuals found at 15 and 20 m depths (Fig. 2).
Sponge biomass on the Hengam Island shows a significant relationship
to depth at each region (Table 1). Mean wet biomass
of individual sponges varies with depth. In two regions of Hengam Island,
biomass is greatest at 20 m depth and low at 5 m depth. Mean weight of
individuals sponges was 89 g at 5 m and 249 g at 20 m depth (Fig.
3). The sponge fauna on the East and West of the Hengam Island was
seven species. Sponge species on Hengam Island consist of Callyspongia
clavata, Callyspongia vasselli, Hyrtios erectus, Haliclona
sp., Leucetta sp., Ircinia echinata and Dysidea cinerea.
| Table 1: | Results of analysis variance on individual abundance and total sponge biomass on two regions and depth of Hengam Island |
Sponges are clearly an important component of benthic communities in
the Hengam Island. This study is the first one to investigate for sponges
distribution within Hengam Island in the Persian Gulf. In this survey
sponges fauna on the East and West of this region at 5-20 m depths was
seven species. The abundance and biomass of sponges differ with depth
on Hengam Island in the Persian Gulf. Biomass and abundance of sponges
shows significant with depth (Table 1). The variation
in abundance of sponges species at depths could result from biological
and physical factors such as degree of physical turbulence, light transmittance
(Wilkinson and Cheshire, 1989). Both decrease with depth and both are
able to affect sponge populations (Wilkinson and Evans, 1989). Water turbulence
and UV radiation can also influence sponge distribution, restricting some
species to less-turbulent area where physical damage is less or to areas
where radiation levels are low (Jokiel, 1980; Wilkinson and Trott, 1985;
Wilkinson and Evans, 1989; Bell and Barnes, 2003; Duckworth and Wolff,
2007). UV light could inhibit the growth of some sponges within the first
10 m depth, but, growth did occur where the sponges were shielded from
UV light (Jokiel, 1980). Over variable depth, this generally results in
highest sponge abundance in deeper water where levels of water turbulence
and radiation are lower (Wilkinson and Evans, 1989; Diaz et al.,
1990; Schmahl, 1990a, Roberts and Davis, 1996; Duckworth and Wolff, 2007).
Wave-induced turbulence is possibly a factor which limits sponge growth
in exposed, shallow water habitats (Palumbi, 1984; Wilkinson and Evans,
1989). Few sponges can withstand strong turbulence and sponge populations
increase markedly below 10 m where effects of turbulence are attenuated
(Wilkinson and Evans, 1989). Sponges in shallower waters are probably
preyed upon by fish and turtles; however, predation was not apparent at
greater depths (Wilkinson, 1982). There are Hawksbill turtles (Eretmochelys
imbricata) in the Persian Gulf (Hengam Island) (Mobaraki and Elmi,
2005). They are major predators of sponges at shallower waters in this
Island. This may explain the high abundance of sponges at 15-20 m depths
on the Hengam Island. With species surveys at both region of Island, it
was distinguished that all species had similar distribution on the West
and East of the Hengam Island. This case indicated that similar environmental
factors influence on sponges distribution in this Island. In conclusion,
sponge distribution on Hengam Island correlates with depth. Turbulence
and light decrease with increasing depth and both appear to be important
factors in determining sponge abundance and biomass. Therefore abundance
and biomass of sponges increase with increase depth in Hengam Island (Table
1, Fig. 2, 3).
| Fig. 2: | Mean abundance of sponge species on four depths of East and West on Hengam Island. (A) 5 m, (B) 10 m, (C) 15 m and (D) 20 m. sp. 1: Callyspongia clavata, sp. 2: Hyrtios erectus, sp. 3: Ircinia echinata, sp. 4: Callyspongia vasselli, sp. 5: Leucetta, sp. 6: Dysidea cinerea, sp. 7: Haliclona sp. |
| Fig. 3: | Sponge biomass at 5, 10, 15 and 20 m depth on the East and West of Hengam Island |
ACKNOWLEDGMENT
I am grateful to the Kaveh Samimi Namin for diving activities.