{'fraction_non_alphanumeric': 0.027614571092831962, 'fraction_numerical': 0.0, 'mean_word_length': 5.2153284671532845, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Allelopathic Inhibitory Effects of the Dried Macroalga Ulva pertusa on the Photosynthetic Activities of Red Tide-Causing Microalga Skeletonema costatum

Allelopathic effects of dried macroalga Ulva pertusa (Chlorophyta) on photosynthesis of the microalgae Skeletonema costatum (Bacillariophyta) were evaluated using coexistence culture systems. S. costatum was cultured with different biomass of dried U. pertusa under controlled laboratory conditions for three days. The chlorophyll a (Chl a) fluorescence transient O-J-I-P curve coupled with its specific parameters in S. costatum was established. The oxygen evolution rate was measured, the Chl a fluorescence transients were recorded in vivo at high time resolution and analyzed according to the JIP-test which can quantify photosystem II activity. A clear dose-dependent relationships were observed between the dried biomass of U. pertusa and its inhibitory effect on S. costatum. The rate of light-saturated maximum photosynthetic oxygen evolution (Pmax) was markedly decreased by different biomass of dried U. pertusa, while dark respiration rate (Rd) was increased. A decrease in the O-J-I-P curve expressed as Chl a fluorescence intensity along with its specific parameters were observed, which was also time-dependent. The main photosynthetic inhibitory targets of the macroalga on the microalga, according to oxygen evolution rate and the JIP-test, can be expressed as, the damage to the oxygen-evolving complex, a decrease in the number of active reaction centers and the blocking of the electron transport chain. The results of the present study suggest that dried fragments of U. pertusa effectively inhibit photosynthesis in S. costatum.