MUCILAGE FORMATION and ITS EFFECTS on the SEA of MARMARA (part-4)

2.4. Mucilage effects to marine environment

 Marine mucilage does have a variety of harmful effects. There have been many studies on the formation of marine mucilage and it creates social and economic concerns and problems in many areas such as coastal areas, maritime transport and fisheries.The effects of mucilage are listed as follows:

1. Extinction of aquatic life

2. Fishery

3. Tourism

4. Maritime transportation and vessels

5. Release of harmful gases into the atmosphere

 The correct strategy is to eliminate the elements that cause mucilage formation before it occurs; otherwise, the only option is to collect mucilage from the water using different marine boats and technologies. Observation of mucilage in the Turkish Straits and potential causes determined the marine pollutants that can cause mucilage as follows:

·      Pollution from household waste that occurs due to the direct or indirect mixing of wastes such as sink wastes into the sea, with or without treatment in sewage systems.

·      Pollution from industrial wastes that arises when industrial wastes (cooling water and chemical wastes including heavy metals and chemicals) from 143 densely located industrial facilities along the Marmara Sea reach the sea after being directly/partially treated/purified.

·      Agricultural waste caused by chemical fertilizers and pesticides used in agricultural activities reaching the sea in various ways.

·      Pollution from ships and marine vehicles.

·      Waste and pollution transported from other seas by surface and

·      undercurrents transferring pollutants and microplastics to the Sea of

·      Marmara due to the interconnection of seas and rivers.

·      Other waste due to air pollution, which is not mentioned in the above articles, direct pollution of the seas by waste, dust, pollen, etc.

 Maritime operations on ships are very hazardous and need tremendous caution. The implications of any faults in these operations, which should be carried out with precisely by the whole ship crew, might be catastrophic. There are also uncontrolled external variables that impact marine operations, such as weather, environmental issues, warfare, etc. Mucilage is one of these external variables affecting ship operations, and it has recently caused considerable challenges for ships navigating through the Turkish Straits and the Sea of Marmara. When analysing the effects of mucilage on ship operations, whether directly or indirectly, it is obvious that the effect of mucilage on systems operating with seawater will be higher. These systems are listed below: Seachest Filters: In seachest filters, the mucilage settled in the filter pores can clog the filter in a short time and causes the flow of seawater to decrease. Figure 2.8 depicts the seachest filter of a ship sailing through the mucilage area.

 Seachest Filters: In seachest filters, the mucilage settled in the filter pores can clog the filter in a short time and causes the flow of seawater to decrease.

Figure 8 Seachest Filters after mucilage

All systems that operate with seawater on ships sailing in mucilage area are likely to be adversely affected. In conclusion, the following impacts are very likely to be observed in ship operations;

·      Even though mucilage is hard to remove from surfaces, it accumulates a layer on the filters and coolers.

·      Mucilage causes heat to build up in ship machinery, decreasing machine efficiency.

·      In heat exchangers, mucilage causes insufficient flow.

·      Mucilage causes filter blockage.

·      Corrosion is caused by mucilage.

·      Mucilage clogs the hull and cooling pipes as it settles.

2.5. Bacterial Levels in Mucilage; Sample Case of Preliminary Study in Istanbul Province, The Sea of Marmara

Marmara Sea in the coastal area of Istanbul Province in April and May 2021, the Zeytinburnu coast, where Çırpıcı Stream empties into the Marmara Sea, the Violet coast, which is the connection point of the Küçükçekmece Lagoon to the Marmara Sea, the Bostancı coast, Pendik Marina, Dragos Marina, Moda Pier and the Marmara Sea of Kurbağalıdere River sea water and mucilage samples were taken at the Kadıköy coast where it empties into the Sea (Figure 2.8).

Figure 9 Stations of sea water and mucilage sampling stations

 Bacteria, which play an important role in the degradation of organic matter, are the most

Important components of the marine ecosystem. The metabolic responses of bacteria to environmental changes determine the processes that will affect the sustainable use of the ecosystem. A healthy marine ecosystem can be defined by a healthy microflora. For this reason, associating the bacteria in the mucilage with the dissolved carbohydrate level in the environment is important in terms of establishing links for the bacterial consumption of the accumulated organic matter. In this study, preliminary data of bacteriological analyzes of mucilage taken from different points in the coastal area of the Marmara Sea and Istanbul province between April and May 2021 and of seawater samples surrounding the mucilage are presented. While the average total heterotrophic aerobic bacteria (HAB) level determined using the smear plate technique was 63x1012±1.6/ml in mucilage samples, the highest HAB level was recorded as 74x1014±1.24/ml. Indicator bacteria indicating the presence of pathogenic bacteria were found above the limit values ​​in all samples. The mean total dissolved carbohydrate level in the samples taken from mucilage and surrounding sea water was recorded as 68±0.5 and 29.5 ±00.3 mg/L, respectively. Preliminary bacteriological data were compared with the bacteriological data obtained from the mucilage observed in the Marmara Sea in 2007 and 2010, and heterotrophic bacteria levels detected higher in the mucilage sample than in sea water were evaluated as bacterial affinity for the dense polysaccharide content in the mucilage. Preliminary findings suggest that bacterial consumption of mucilage caused by accumulated/slow degrading organic matter should be considered in conjunction with other components in the biomass.

Figure 10 Some images from Sampling Stations (a) Pendik Marina 1 b) Zeytinburnu c) Pendik Marina 2 d) Küçükçekmece Lagoon-Marmara Sea connection May 2021

2.6.Sea Snots in the Marmara Sea as Observed From Medium-Resolution Satellites

 Multisensor medium-resolution satellite images from Moderate Resolution Imaging Spectroradiometer (MODIS), Visible Infrared Imaging Radiometer Suite (VIIRS), Ocean and Land Color Imager (OLCI), and Medium Resolution Imaging Spectrometer (MERIS) are used to study spatial and temporal distributions of sea snot features in the Marmara Sea between 2000 and 2021. Suspicious image slicks are identified in most years, and spectral diagnostics indicate sea snot features in 2007, 2008, and 2021, with the record-high sea snot event occurring in spring-summer 2021. In other years, when similar image slicks are found, they appear to be from surface scums of red Noctiluca scintillans, a heterotrophic dinoflagellate responsible for red tides. Based on the medium-resolution images, the 2021 sea snot event started from March 14 and ended on June 27, with its peak time around May 4 when the sea snot features are found in the entire Marmara Sea covering an area of 1160 km2. When all sea snots are aggregated together, the estimated areal coverage during the peak time is 50 km2, suggesting significant patchiness in the surface scums. [24]

 Although all optical satellite sensors can be used to observe water lilies to form a long-term sequence with frequent observations, only the moderate resolution satellite sensors are used in this study. These include the Moderate Resolution Imaging Spectroradiometer, the Medium Resolution Imaging Spectrometer, the Visible Infrared Imaging Radiometer Suite, and the Ocean and Land Color Imager. They have multiple spectral bands that measure reflected sunlight at a nominal resolution of 250 to 375 m, with other bands having resolutions of 500, 750, or 1000 m.

Figure 11 (a) and (b) Demonstration of remote detection of sea snot features and (c) and (d) discrimination from Noctiluca-like features in the Marmara Sea. (a) and (b) MODIS/A and OLCI/3A FRGB images on May 13, 2021 showing surface slicks in the Marmara Sea, where the spectral shapes (inset figures) of several randomly selected pixels show typical sea snot characteristics. The three locations (“1,” “2,” and “3”) in both images are identical. The dashed rectangle outlines a region of surface snot and subsurface snot features. (c) and (d) MODIS/T and MERIS FRGB images on May 21, 2004 showing similar surface slicks as in (a) and (b), but their spectral shapes (inset figures) indicate typical RNS characteristics. The three locations (“4,” “5,” and “6”) in both images are identical. The white colored patches over the water in (d) are due to sun glint as opposed to clouds. Because of the small size of these surface features, only MODIS 250 and 500-m bands are used here to show the spectral shapes [insets of (a) and (c)]. The inset figure of (d) shows annual occurrence of RNS and snot features with three scales: small (features found in <1/4 of Marmara Sea), moderate (between 1/4 and 1/2), and large (>1/2).

Figure 13 Evolution of the 2021 sea snot event during (a) first half and (b) second half. The colored outlines show the approximate water boundaries, within which sea snot features are found in satellite imagery

Figure 14 Time series of (a) mean wind speed and PAR and (b) mean SST and Chl for the Marmara Sea, all obtained from NASA Giovanni. The data were partitioned to February–March and April–May in order to examine potentially anomalous conditions for the 2021 sea snot event.

Figure 15 Illustration of (a) possibly submerged sea snot features and (b) their corresponding spectra. The image in (a) is a small region in Fig. 2.10 (b) (May 13, 2021) but enlarged to show the whitish slicks (sea snot on water surface, with a sample point marked as “X”) and pinkish patch (dashed arrow). The spectra in (b) were extracted from the surface snot feature (“X”) and the pixels along the dashed arrow in (a). The rapid decrease in the wavelengths above 620 nm appears to be due to strong water attenuation of reflectance from submersed sea snot features, whose estimated depths are annotate.