*2.1. Mariculture Sites and Monitoring of Water Quality*

All of the studies were carried out in the coastal waters around the Bodrum Peninsula, Southwest Turkey (Figure 1). Meteoroloji Bay (Figure 1 Pr.1), a shallow area with an abundant population of *C. reniformis* was selected as a pre-culture and initial testing site (Trial 1). Based on water visibility (Secchi disk, cf. [37]) and organic loading (total organic carbon (TOC) measurements), two additional sites were selected for subsequent testing (Trials 2 and 3): Kargi Island (Figure 1 Pr. 2) at the Southern side of the Bodrum Peninsula was selected as a pristine site, whereas Guvercinlik Bay (Figure 1 Po. 1), located at the Northern side of the peninsula, was selected as a polluted site.

Water temperature (Uwatec Aladin Air X Nitrox dive computer, calibrated with mercury thermometer) and visibility were measured 17 times during periodic visits at the polluted site throughout the experimental period from April 2011 to December 2013. To determine organic loading, three replicate water samples (50 mL) were taken within 10 m from the culture platforms by SCUBA diving from each location for TOC analysis using the wet oxidation method [38]). TOC samples were stored in pre-combusted (450 ◦C for 6 h) 50 mL glass bottles with glass caps at −20 ◦C until analysis. Prior to analysis, sulphuric acid was added to the samples (end concentration 2 mmol L<sup>−</sup>1) to remove dissolved inorganic carbon species. The acidified samples were supplemented with sodium tetraborate and potassium persulphate and processed using segmented flow analysis (SFA) on a Continuous Flow Analyser (Skalar, Breda, The Netherlands). In SFA, TOC is first oxidized using UV light and then measured as CO2 while using infrared detection. The TOC detection limit of the method, as intercalibrated with other labs, is 25 μmol L<sup>−</sup>1, the average TOC variation among replicate measurements is 10 μmol L<sup>−</sup>1. The internal standards used were 3.3 μmol L−<sup>1</sup> EDTA, 3.3 μmol L−<sup>1</sup> of a humic acid, and 3.6 μmol L−<sup>1</sup> phenylalanine.

**Figure 1.** Map of the Bodrum Peninsula. Small white circle (Pr.1: Pre-culture site—Meteoroloji Bay). Large white circles (Pr.2: Pristine—Kargı island) and large black circles (Po.1: Polluted—Guvercinlik Bay) circles point the approximate locations of the sites used for growing sponge explants in this study. GPS coordinates 36.9444444, 27.27611111; 36.95166667, 27.30694444; 36.96861111, 27.45083333, respectively. (Source: Google Earth, 2018).

#### *2.2. Sponge Collection and Seeding*

Sponge specimens were collected by SCUBA at 5–10 m water depth in the Bay of Meteoroloji (Figure 1 Pr.1). Explants were cut with sharp razor blades and detached from rock surfaces with a spatula [8,39], leaving the majority (at least 75%) of the donor sponge unaffected. The explants received maximally two cut surfaces and more than 50% of their surface was always covered with intact pinacoderm (i.e., the sponge outer tissue layer). The explant size ranged between 10–15 cm<sup>2</sup> with an average thickness of 2 cm, and all of the explants had at least one osculum (i.e., outflow opening). Explants were stored in perforated plastic containers that allowed water flow and they were left underwater until the seeding operations started. To enable sponges to attach and acclimatize after seeding, the seeding plates with the explants were left horizontally next to the culture platforms for three days before the plates were secured to their spots on the culture frame [14].
