Impact of climate change-induced temperature and salinity fluctuations on mussel byssus production and attachment...

Climate-induced fluctuations in temperature and salinity are critical stressors affecting mussel survival, attachment, and byssal thread production, all of which are vital for the success of longline aquaculture operations. This study examines the combined effects of two temperatures (21 °C and 29 °C) and six salinities (5, 10, 15, 20, 25, and 30 psu) on mussel survival, byssal thread production, attachment strength, byssus mechanical properties, and histological changes in foot secretory glands. The results reveal distinct impacts of these stressors: survival was highly dependent on salinity, with a strong positive correlation observed, whereas detachment was primarily influenced by elevated temperatures. Exposure to 29 °C resulted in catastrophic detachment, reaching 54.7% at 5 psu, and mass mortality at low salinities. Byssus secretion was completely absent at salinities of 5-10 psu, initiated at 15 psu under control conditions (21 °C), but was delayed to 20 psu when the temperature was elevated to 29 °C. Furthermore, the byssal breaking force and plaque adhesion strength were significantly compromised under higher temperatures. Histological analysis revealed that the total foot gland, collagen gland, and dopaquinone regions decreased significantly in size under thermal and low-salinity stress, with the most pronounced reductions observed in the collagen and dopaquinone regions at higher temperatures, which may be associated with reduced byssus performance. These findings suggest that elevated temperature promotes mussel detachment, while reduced salinity severely impairs survival and byssus secretion. By investigating the interactive impacts of these two climate-driven stressors, we have filled a research gap concerning the large-scale detachment events at Lvhua Island, revealing that temperature, rather than salinity, is the primary driver of mussel dislodgement.