Moscow — Four developments here indicate the relentless Kremlin crackdown on dissidents is still going strong in advance of the Moscow Olympic Games and in defiance of US and West European opinion:
On his way to a polyclinic on a quiet street in the Estonian university city of Tartu, ornithologist and language teacher Mart Niklus is suddenly arrested and taken to jail for the second time in two months.
Going to work at a scientific institute in the city of Kalinin north of Moscow, geophysicist Yosif Dyadkin is seized. Later his apartment is searched and papers taken.
In Moscow itself, KGB agents arrest mathematician Alexander Lavut after his apartment and those of two friends have been searched.
And in Section 35 of labor camp No. 389 in the Urals city of Perm, east of Moscow, the best-known of all the jailed dissidents, Anatoly Shcharansky, has an emotional reunion with his mother and brother. For 24 hours they talk without rest or sleep. He reports better health, days filled with work in a metal-working machine shop, and a mental resignation to serving his full sentence, which runs until 1990.
Since last November, about 45 dissidents have been arrested, tried, or exiled -- led by the 1975 Nobel Peace Prize winner Dr. Andrei Sakharov, but also including human-rights and religious activists.
Many have been seized in the cities in which Olympic Games events will be held beginning July 19: Moscow, Tallinn, Leningrad, Minsk, and Kiev. The exiled Vladimir Bukovsky, swapped for Chilean communist Luis Corvalan several years ago , said in Brussels recently that "the geography of arrests closely follows the geography of the games."
Since detente began to unravel in late 1979, the Kremlin has been noticeably less worried about Western criticism. President Carter has lost whatever influence he had to "protect" dissident leaders such as Dr. Sakharov, who now sits in the city of Gorky, isolated from all Western contacts, wondering whether emigration might not be preferable to soliditude after all. He is forbidden from visiting Moscow or even telephoning here.
Activists still free here report official harassment and warnings to leave the city before and during the Olympic Games, which are still expected to bring many tens of thousands of foreign visitors here, especially from Western Europe.
Jewish emigration, which topped 50,000 last year, has dropped by about one-quarter in the first three months of this year -- from 12,100 a year ago to 8,695 this year.
Clearly the Soviets want to take advantage of the crumbling of detente (or at least, hardline KGB officials do) to try and clear away as many dissidents as possible. They also want to prevent large numbers of contacts between dissidents and foreign visitors, especially Jews, here during the Olympic Games.
Estonian Mart Niklus served a 13-day sentence for vagrancy in March, and contracted a back ailment. Released April 1, he spent 22 days in hospital in April, and was on his way for more treatment when arrested April 29 in Tartu.
A strong supporter of Baltic independence, he was fired from his post as a language teacher at a Tartu night school after joining 44 others in Estonia, Latvia, and Lithuania in signing a "Baltic appeal" last August.
A fellow Estonian dissident, Dr. Juri Kukk, was arrested recently and is being held in Tallinn, the Estonian capital on the Gulf of Finland, where the Olympic yachting regatta will be held.
Mr. Dyadkin, a veteran activist, recently wrote to several Soviet newspapers protesting the internal exile of Dr. Sakharov. He is said to have been charged with anti-Soviet slander, which could mean up to three years in jail.
Mr. Lavut had been linked with the group of dissidents monitoring Soviet compliance with the Helsinki human-rights accord and had also worked on behalf of the Crimean Tatars, who want their own lands back after being forcibly deported to Central Asia during World War II.
News of Anatoly Shcharansky, whose name has come to symbolize the human-rights clash between Washington and Moscow, came April 29 from his brother Leonid and his mother, Ida Milgrom.
For three years their visits have been restricted. Since his trial in the summer of 1978, they had been allowed only one visit a year. Their recent visit to Perm should have been for three days, but camp officials cut it to 24 hours, claiming Mr. Shcharansky had violated prison rules in his previous camp in Chistopol, 500 miles east of Moscow.
His mother and brother reported him thin but mentally strong. The food in the camp was somewhat better than in Chistopol. He asked avidly for news of Dr. Sakharov and of Jewish emigration. Told that more than 50,000 Jews emigrated last year he remarked, "So it has not all been in vain."